Allergy Problems in Dogs



Pruritis is the name for itchiness that causes pets to scratch. Several chemical reactions occur in the skin that stimulate the nerves, causing the brain to feel the itch. We treat a scratching pet by attempting to eliminate these reactions at the source and controlling the body's response to them as well.

Some of the chemicals involved in itching are prostglandins, arachodonic acid (a specialized fatty acid) and leukotreines. By using treatments that inhibit the action of these factors at the skin level, such as antihistamines and fatty acid competitors, we can sometimes control the itching without using corticosteroids such as prednisone. If we work to control other irritating factors such as fleasdry skin and secondary bacterial infections we can also further reduce itching. Each of these steps is very important because pets have an "itch threshold". This is the point where all of the sources of itching finally add up to enough irritation to cause the irresistible urge to scratch. Just like pain thresholds, these levels vary from pet to pet. Control of every factor that possible is important to your dog's health and comfort. Pruritis is a complication of many diseases. Only by careful examination, diagnostic tests and sometimes even trial and error can we come to understand what causes the itching in a particular pet and how we can best control it.
Mike Richards, DVM



Treatment and Relief for the Itch

Cold water will usually reduce itching and produce temporary relief. It doesn't really matter how the water is applied, but it must be at least cool. This effect doesn't last long, usually less than one-half hour. Adding Episoothe Oatmeal Shampoo, Episoothe Oatmeal Creme Rinse, Aveeno Colloidal Oatmeal, Relief Shampoo or Domeboro's solution helps to prolong the effect. All of these products are available over-the-counter. If you use Aveeno, one to two tablespoons per gallon of water, applied as a rinse, works best. Follow the directions on the Domeboro packet and also apply as a rinse.

Shampooing will sometimes help to control itching. Some shampoos such as Pyoben and Oxydex, act to reduce the bacteria level on the skin, one cause of itching. Seba Lyt and other sulfer/salicyclic acid shampoos reduce scaling. Lytar, Clear Tar and other tar containing shampoos reduce itching and oiliness. An emollient or moisturizer used after shampooing will restore some moisture to the skin and this also reduces itching. Expar Creme Rinse can be used to kill fleas after itching and moisturize the skin.

Antihistamines are useful in the treatment of itching in some dogs and cats. Used alone, about 15 to 25% of dogs will respond to antihistamines. Used in combination with fatty acid inhibitors, such as DermCaps, EFA-Z and Omega EFA capsules, about 25 to 40% of dogs will respond, reducing scratching behavior to acceptable levels. Antihistamines available over-the-counter are Benedryl (diphenhydramine, 25mg capsules) and Chlortrimeton (chlorpheniramine maleate, 4mg tablets). There are prescription antihistamines, notably Atarax (hydroxyzine) that work better in some cases. It is necessary to get a dosage for your particular dog or cat from your vet.

Dogs and cats have individual reactions to antihistamines. Since some dogs will respond better to one than another, it is best to try more than one antihistamine before giving up on them to control itching. Some pets will become drowsy when taking antihistamines. If this is unacceptable, they can not be used, or might be best to use at bedtime. Occasionally a pet will get excited when given antihistamines. These pets should not be given these products.

Fatty acid derivatives compete with aracadonic acid, the trigger for itching in the body. By replacing this compound with an inactive competitor, itching can be reduced. It is important that the fatty acid derivative chosen have gamma-linoleic acid, eicosapentanoic acid, or both. These products work best at high dosage levels and when given with a low-fat canned food such as W/D, which is available through veterinarians. Although they can be fairly expensive, their use is preferable to cortisones if they are effective. It is necessary to use these products for at least 6 to 8 weeks to judge their full effect. EFA-Z and DermCaps are examples of these medications.

Antibiotics are used to control skin infections associated with scratching. The itching leads to scratching, which damages the skin. The damaged skin is easier for bacteria to grow in. The bacteria then contribute to the itching, leading to more skin damage. As this cycle progresses, deeper and deeper layers of the skin are affected, sometimes leading to systemic bacterial infections that can even be fatal. Control of skin infections with antibiotics takes time. The usual defense mechanisms of the body, fever, white blood cells and antibodies do not work as well on the skin surface. Antibiotics must do more of the work alone. For this reason, 3 weeks is the minimum recommended time that antibiotics should be given for skin infections. Often, antibiotics must be continued for up to 8 weeks to consistently control skin disease. Several antibiotics seem to work consistently in skin disease. When these antibiotics fail, it is necessary to culture the skin lesions to identify which antibiotic might be appropriate in an individual case. Occasionally it is necessary to continue antibiotic therapy indefinitely to control severe bacterial skin disease.

Some dogs appear to be unable to prevent penetration of staph (staphylococcus) bacteria into the skin. These dogs can be benefited by the use of a product to promote immune responses. Similar to vaccinations (but short acting), these products help the body learn to fight off staph bacteria. They are Staph Lysate and Immunoregulin. Although somewhat expensive and necessitating weekly injections, these products can cost less to use than frequent or continuous antibiotic therapy. We have better success with Staph Lysate.

Hyposensitization, or allergy "shots", are used in dogs. Their use in cats is very limited due to difficulties testing cats accurately for individual allergens. Similar to their use in people, these injections help many pets, but not all. To be used properly, it is necessary to identify the allergy agents affecting a dog and then treat accordingly. This can be done by skin testing, where small quantities of allergens (allergy causing agents such as pollens), are injected into the skin and the response to this monitored. Often, it is necessary for a general veterinary practitioner to refer a pet to a veterinary dermatologist for this testing. Recently, blood tests have been developed to allow allergy testing without injections into the skin. These have become better understood recently and are correlating with the skin testing fairly well, although it is generally agreed that skin testing is still more accurate. Allergy injections require a consistent effort from the pet owner. They are the preferred treatment for inhalant allergies if that is the only condition affecting dog, when effective. Currently, about 70% of dogs are thought to benefit from this therapy.

Fleas cause most the allergic reactions in pets. Flea control is essential to our success in treating itchy dogs. Please ask for flea control information if you have any problem at all with fleas on your pet!

When itching can not be adequately controlled by one of the above methods, we usually use a corticosteroid, such as prednisone. Cortisones are the most consistently effective anti-itch medications that we have. They do have several drawbacks, however. Cortisones increase the amount of water your pet drinks, making it urinate more, too. Sometimes this becomes a problem. These drugs increase appetite and weight control can be difficult while using them. If proper dosage schedules are not followed there can be long-term side effects such as decrease in bone density or an increased chance of pancreatitis. Cortisones depress lymphocytes, a type of white blood cell, making it easier for bacterial infections to occur. Accidental overdosage with these medications or inappropriate long-term use can lead to medication induced Cushing's disease, a cause of hair loss, muscle weakness and other problems. For these reasons, most vets insist on monitoring a pet on cortisones through follow-up office visits. You may be required to allow examination of your pet prior to refilling prescriptions for these drugs.

In spite of these side effects, cortisones can be the best drugs to make an extremely itchy pet comfortable. If they are the only effective drugs for your pet they are worth the small risk to an individual pet of side effects. These drugs are reasonably safe for long term use if given according to directions. Allowing your pet a good quality of life, by controlling the itching, is worth the small risk of using prednisone and related compounds.

These are the methods we use to treat pruritis, the itchiness that causes your dog or cat to scratch. It may take several tries to work out the proper drug and dosage schedule for your pet, but is worth the effort. 

Mike Richards, DVM



Determining Food Allergies with A Food Trial

Q: Dr. Richards,

It has become more apparent that my two dogs probably have some kind of food allergy. And the situation has not gotten any better. Sometimes they both scratch "like crazy" and they at times struggle to try and get to the base of their tail.

I understand that there is a method called the elimination diet. I'm not sure exactly what this is, but I get the sense that the dog is fed the same diet (deficient) for 90 days? It seems that if one wanted to determine if a certain food was the cause of an allergic reaction, one would begin by starting the feeding for a number of days with one type of food the dog can eat and then start to add other foods one at a time to determine if there is any kind of a reaction. But is it not also true that it could be up to a week before the dog would show any signs of an allergic reaction? I need to provide these pets with some kind of relief.

Tony A.

A: Tony-

The problem with determining if food allergies are present is that dogs are usually allergic to only one ingredient, or to a small number of ingredients -- not to the whole diet. So the problem becomes isolating the food that is causing the problem.

This has traditionally been done by making a diet that is composed of foods that a dog has never eaten before. Since food allergies are thought to occur only to foods that the dog has been sensitized to, there should not be an allergic reaction to a food that has not been eaten previously. An early diet to achieve this purpose was lamb and rice but now both of these ingredients are used in other dog foods and so this combination is less likely to be helpful. More exotic protein sources like ostrich meat, alligator meat, duck, venison, rabbit, etc. are usually used and potato, peas and rice (still) are sometimes used as the carbohydrate source. A homemade diet with these ingredients and no supplemental calcium or vitamins will be deficient as a long term diet but is usually OK for short term use in adult dogs or cats.

A newer approach is to use a diet composed of artificially created very low molecular weight proteins. The reason for this is that proteins below a certain molecular weight are thought to be incapable of causing food allergies. Hills z/d (tm) diet and Purinas HA (tm) diet are made from hydrolyzed proteins. These diets should be a very good choice for determining if a food allergy is present and should be more reliable than novel protein diets, at least in theory. They are relatively new diets, though.

If clinical signs disappear while your dogs are on the diets, which may take 8 weeks or more, then it is reasonable to assume a food allergy is present (although with approaching winter it will be hard to totally rule out inhalant allergies or atopy).

Food ingredients such as beef, chicken, milk, wheat, corn, etc. are added back into the diet one at a time to see if clinical signs return. If and when they do, it is reasonable to assume that the ingredient being added at the time is the cause. Future diets shouldn't include this ingredient.

It is a really good idea to rule out food allergies when itchiness persists for a long time, so choosing to do a food trial to rule out food allergy is a good option.

Mike Richards, DVM



Preventing Ear Infections from Allergies 

Q: Maisey, our ten-year-old Shih Tzu, suffers from allergies. I try to keep them under control with high-quality food, bathing, etc. But the most troublesome aspect for her seems to be ear infections. Her ears become red and swollen and she scratches at them, often whining with pain. When this happens I use Tresaderm which works pretty well to relieve the swelling and pain. However, my vet tells me that Tresaderm won't prevent the infections, but will only relieve them once they occur. Is there something I can use on a regular basis to prevent the ear infections in the first place?

A: Anne-

Since the infections that occur in dogs with ear allergies get their foothold due to the inflammation from the allergy, anything you can do to control the inflammation will help prevent the infections. We have the best luck with the following things:

1) Hyposensitization, which is the injection of very small amounts of the substance that the patient is allergic to, so that a tolerance to the substance develops. We have three or four patients who have responded really well to hyposensitization. We send our patients to a veterinary dermatologist to determine what they are allergic to through skin testing and the dermatologist mixes up the injections based on what he finds. This usually costs over $500 for the first year and works about 80% of the time, so we think of it as a better option for a young dog but there is reason it couldn't work with an older patient.

2) Rinsing the ears with white vinegar mixed 1:1 with water, or one of the acetic acid preparations available commercially, once or twice a week, will often help a great deal in reducing the infections.

3) Using Synotic (Rx), or another corticosteroid otic preparation whenever the ears seem inflamed at all will help in some dogs to control secondary infections. Oral corticosteroids will also work in many dogs but have more of a chance of causing systemic side effects.

4) Some dogs respond really well to antihistamines or antihistamine/essential fatty acid supplementation. The most successful antihistamine in clinical trials is clemastine (Tavist Rx) and it works well enough to prevent ear infections in about 20 to 30% of dogs.

5) There are some commercial ear medications that contain both acetic acid (vinegar) and a corticosteroid.

6) The otic preparations containing an antibiotic, antifungal and corticosteroid can be used on an intermittent "as needed" basis to control inflammation. This works pretty well as long as they are started at the first sign of trouble and used for a least five to seven days. We use Tresaderm Otic (tm) in this manner in some patients. Hope this helps some.

Mike Richards, DVM



Homemade Diets for Cocker with Allergies

Question: Dear Dr. Mike. As you must have gathered by now, I am not an experienced E-mail sender. My problem concerns my sweetest American cocker called Pesie. She is 9 and 0ne half years old. She has brought us a lot of pleasure, but has been most troublesome health wise with her allergies. we have gotten by with antibiotics and anti fungals, both by mouth and topically applied. She originally had the skintest, which turned out to be negative. We have used up all the known protein sources short of kangaroo, which I will not, on principal give her. My vet suggested a new food which has a genetically altered protein source. Sounds awful! What do you think of this? She likes homemade food. The last few weeks, she has been on rice and chicken, which she likes. How about a longterm hypoallergenic diet which I can make at home. Any recipes to share with me?

Answer: Dawn-

If you have tried more than one protein source and if you have truly limited Pesie's access to food so that she only got the one protein source during the dietary trials (no treats, no access to the cat food, stuff like that), then I don't see any point in trying again. Food allergies are almost always to common protein sources like beef, chicken, milk, soybean, wheat or corn. Once you have tried a protein source that is not one of these and used it for at least six weeks, it becomes unlikely that a food allergy is present. The new diets composed of hydrolyzed proteins make it possible to feed a food that is extremely unlikely to cause an allergic reaction but given the track record of restricted diets, so far, I have real doubts that Pesie will benefit from this sort of dietary change.

If you want to make a diet at home, I can provide some guidelines but I'd have the same feeling about the chance for success. It sounds like you have tried a food trial, it didn't work, and it is time to move on to other possible problems.

Cockers are prone to primary seborrhea (improper production of skin oils) which leads to chronic skin disease. Sometimes Vitamin A supplementation will help with this problem. Retinoid medications such as isotretinoin (Accutane Rx) and etretinate ( Tegison Rx) have been used with some success in dogs but are pretty expensive. It obviously isn't possible to make a diagnosis of seborrhea without an examination but you might want to ask your vet about this possibility.

Mike Richards, DVM



Allergies Mixed with Thyroid Tests and Keflex

Q: I have a 7 year old, spayed golden retriever. She has always bitten and scratched herself excessively. The summer she was 3 it was so bad, her intire neck / chest area was totally raw and looked like an open sore. I switched her flea med. from Program to Advantage and she made a complete recovery. She still scratches and bites a lot, just not quite as bad as she used to. She started chewing her tail and back really bad at the beginning of the summer (this year) and my vet gave her a cortisone shot and it helped for a couple of months, but now that the shot has worn off, she's at it again. Since then she has also developed an ear infection (not uncommon). When I took her in to get an antibiotic for her ears, we talked about really getting to the root of the problem. He thinks the ear infection and skin problem are related. He prescribed Otibiotic ointment for her ears and an internal antibiotic called Keflex (500mg / capsule to be taken twice daily for 40 days), gave her another shot of cortisone and also a very strict diet of Iams Eukanuba Response FP formulated for skin and coat. His theory was this was allergies (my thought, too) and we'd give her the antibiotics to clear up the skin and restrict her diet to rule out a food allergy. But here's where I get confused... He also ran a T4 test to eliminate the possibility of thyroid malfunction despite the fact she weighs 74 lbs. She's perfect in weight and size. She's very fit and thin, long legged, and beautiful. The next morning he called me with the results of the T4 test and said she was .7 (whatever that means) and wants to begin lifelong treatment for hyper-thyroid. I think he's a great vet, but sometimes a fast talker (like a car salesman) and a little too excited about prescribing multiple meds. She currently takes Advantage for fleas and Interceptor for heartworm prevention every month. My questions are...

1. What can you tell me about Keflex ? On the side of the capsule is printed Z4074 .Is it supposed to have a strong odor ? Does she really need such a strong dosage ?

2. Explain the thyroid test and it's result in my case. Are there any other tests to back up the T4's result ? How accurate is this test ? What factors would cause an incorrect diagnosis from the T4, such as other meds she's on or what she had eaten recently ? If I do medicate her for this, what are the side effects especially long term on liver and kidneys ?

3. What are the different kinds of allergy tests available ? Would I need to go anywhere special or can my local vet administer them ? How accurate are they ?

4. What is your best hypothesis and opinion on coarse of treatment ?

Thank You, Amy

A: Amy- I'll try to answer your questions in order, as much as is possible.

Cephalexin (Keflex Rx) is usually dosed at 10mg/lb of body weight for skin disease. So the dosage is actually low but since there isn't a 750mg capsule, it is not uncommon for vets to use 500mg twice a day up to about 75 lbs of body weight and then 1000mg twice a day for weights between 75 lbs and 100lbs. I just tend to use the 500mg dose three times a day or give 1 500mg and 1 250mg capsule every 12 hours but I am not sure that it is necessary to stick exactly to the dosage. In any case, the dose is actually lower than normal, not higher.

A total T4 test is an inaccurate method of determining if hypothyroidism is present, unless it is very low. There should be a laboratory normal value, which varies from lab to lab, for this test result. In general, I am not comfortable using a total T4 value to establish the presence of hypothyroidism unless the value is something like 0.1 ug/dl, although values of less than 0.5ug/dl are very suspicious for the presence of hypothyroidism in a dog that has no other systemic illness. It is really important to realize that a concurrent illness, such as severe skin infection, can lead to suppressed total T4 values.

Currently, the most accurate test for determining whether hypothyroidism is present is the free thyroxine (Free T4, FT4) test done by equilibrium dialysis. This test is available through Michigan State University's endocrine lab and probably several commercial labs, as well. When combined with measurement of canine thyroid stimulating hormone (cTSH) it is slightly more accurate, but not enough to make it absolutely necessary to run both tests. A low free T4 combined with a high cTSH level is a very sure sign of hypothyroidism. The free T4 test is also affected by systemic illnesses. The free T4 level is suppressed by the presence of another illness, so this has to be taken into account when interpreting this test. It may be better to clear up as much of the skin disease as is possible and then retest, using the free T4 test by equilibrium dialysis as the testing method. Your vet may feel that the clinical signs and low total T4 test are enough to diagnose this condition but you are looking at a disease that requires lifelong supplementation so I think it is best to be as certain of the diagnosis as is possible.

One reason that veterinarians are willing to supplement thyroid hormone based on the clinical signs and/or total T4 testing is that thyroid hormone supplementation causes very little problem in dogs that do not require the medication. Dogs tolerate administration of thyroxine, even when they don't need it, very well. I can only remember one dog that had any problems as the result of thyroxine supplementation and that dog was just very excitable and restless. Both symptoms resolved when the medication was withdrawn. That still doesn't justify using a medication when it is not needed, though.

The best allergy test is intradermal skin testing, which is usually done by a veterinary dermatologist, although there are a number of general practitioners who do this test, as well. As long as the person doing the testing is experienced, there should be no problem with using a general practitioner's services. It is possible to test for inhalant allergies using blood testing but this is not yet considered to be as accurate as skin testing. It is getting pretty close, though. We have done a small amount of blood testing for allergies, mostly for clients who refused to go to a dermatologist, and we have had reasonable success with the testing. I would still take my dog to a dermatologist for skin testing, though. The only way to measure accuracy is by response to treatment with hyposensitizing agents, which may fail for reasons other than test accuracy. However, skin testing usually results in about 70 to 80% success rate for hyposensitization and serum testing about a 60 to 70% success rate.

In the mid-Atlantic region, I think that all skin disease should be considered to be linked to flea bites, flea allergy and inhalant allergies until proven otherwise.
Mike Richards, DVM



Excessive Licking and Scratching

Q: Dr. Richards,

I have taken my 3 year old yellow lab to the vet twice now for his excessive licking and scratching. The vet gave him a cortisone shot and put him on 3V Caps and prednisone to take over a three month period. The cortisone shot seemed to help for a day or two, but once he started taking the prednisone, he was sleepy most of the time, and drank so much water that he basically became incontinent. I was up 4 or 5 times a night to let him out to urinate and he was urinating in the house if no one heard him ring his bell to go out. (someone is home all day). So basically, the cure seemed worse than the "disease" and I weaned him off the prednisone after about 6 weeks. Besides which, it cost me $200 for the office visits and meds. I need to know what else it could be besides "allergies in August" because this licking is driving me (and the dog) crazy. He licks so loud and long he wakes us up, not to mention his skin and paws look bad where he licks.

Any help would be appreciated. Gayle

A: Gayle- If your Lab is licking a lot but has no visible skin disorder, such as pustules, scabbiness, hairloss or something similar, the odds are really high that your vet is correct about the cause. Even if these other conditions are present, it is highly likely that allergies are part of the problem.

3V Capsules (tm) are currently favored by veterinary dermatologists as they contain a higher percentage of the fatty acids thought to be helpful. It takes several weeks for a benefit to show from essential fatty acid supplementation and not all dogs and cats are helped. Antihistamines used in combination with the 3V capsules may be beneficial. The antihistamine most likely to help, based on studies, is clemastine (Tavist tm). Regular bathing with soothing or antibacterial shampoos can be helpful, although not all dogs are cooperative about this.

If there is a secondary (or primary) bacterial skin infection, then using an antibiotic or antibacterial shampoo might be helpful. In a dog this young, it would be worth considering going to a dermatologist, confirming that allergies are the problem and trying hyposensitization (allergy shots). It works about 70% of the time to control the itching and has few side effects compared to medications. This is costly the first year but over time I think it is less costly and more comfortable for the dog, when it works. Knowing that allergies are present and what the allergies are can sometimes allow better planning for medication use, even if you don't elect to try hyposensitization.

Another alternative is to consider low dose cyclosporin therapy. This is a new approach to pruritis from allergies and there are no really long term studies on its use, but it seems promising based on early information.

It may also be possible to adjust the dosage of prednisone to get some anti-itching effect with less of the side effects, especially if combined with fatty acid supplementation and antihistamines.

Allergies are lifelong and that makes it important to think of the long range effects of everything that is done. It is best to use prednisone for as short a time and at as low a dose, as possible.

I wish I had an easier solution for your problem.

Mike Richards, DVM 9/20/2000



Potential Grass Allergies

Q: Hi Dr. Richards

Earlier this year I asked you about my 2 year old female doberman's ear problems. They were inflamed and she was continuously shaking her head. You suggested it could be an allergy to either her food or the environment. We immediately changed her food to California Natural (lamb & rice) but we have not noticed much of a difference. Now the hair on her chest seems to be thinning. I also sometimes notice the bridge of her nose seems to be a little swollen.

We haven't had allergy tests done on her because I'm now pretty sure she is allergic to grass. Ever since spring every moment she is outside all she does is eat it. She'll even sit in the house and cry just to get outside to eat it. It's like she's addicted to it. We have tried everything to get her to stop with no luck.

Do you have any suggestions?

I've been told it could be because she is lacking something in her system. Could this be true and would vitamins or minerals help?


A: Sheilah-

Grass would be an unusual food allergy, because it doesn't have all that much protein in it, which is the part of foods that usually causes allergic reactions. However, grass pollens are sometimes involved in inhalant allergies and since pollens stick to grass when gravity brings them to the ground, wet grass can sometimes be associated with itchiness of the feet or portions of the body it contacts.

It does sound like your dobe really overdoes the grass eating. Sometimes it is helpful to add something like green beans to the diet in order to discourage this behavior. It seems to meet the need for plant ingestion in some dogs. Other dogs like alfalfa sprouts and we even have one patient who craves lettuce. If there is some sort of deficiency that leads to this behavior it has never been conclusively identified, as far as I can tell.

Hopefully her ears are doing OK through all of this.

Mike Richards, DVM



Skin Allergy Treatment with Glucosamine in Peanut Butter and Benadryl

Q: Dr. Richards:

My 9 year old golden has been having a time w/ skin allergies. I had a groomer recommend giving her a teaspoon of peanut butter a day. Since I give her glucosamine tabs twice a day, I've started hiding them in a little peanut butter. It really seems to be helping w/ her skin.

Is peanut butter all right for her? I really work at keeping her low, and worry that the added peanut butter calories may not be good.

Also, when she's itching I give her Benadryl. Usally 25 mg every 6 hours. She's about 68 lbs. Is this dose all right?

Finally, does the glucosamine have any negative interactions with the benadryl?

Thank you for your response.

A: Vanessa- I know of no reason that you shouldn't give peanut butter to your dog. I suspect that it can cause problems with allergic reactions in dogs, just like it does in people, but that would not be a common problem and if you have no reason to suspect it occurs, it probably doesn't.

If your dog has a weight problem, you would have to subtract the calories it provides from other food or treat items that you give during the day.

The usual dosage range for diphenhydramine, when used for allergies, is 25 to 50mg once or twice a day. Some vets use 1mg/lb of body weight. Using 25mg four times a day would be acceptable, because it is within the daily dosing limit.

I know of no interaction between glucosamine and diphenhydramine and I can't find any reports of interactions, either.

Mike Richards, DVM



Allergic Reaction to Medication?

Q: Hi Dr. Mike: My 5 year old Doberman had a severe allergic reaction (generalized giant hives and swelling of his muzzle) while being treated for giardia diarrhea with metronidazole and imodium. I found no sign of an insect sting so the presumptive diagnosis was a reaction to one of the medications. He is doing fine with an antihistamine (benadryl). I am so worried now that we may forever be restricted from using these very important drugs.


     -is there a reliable way of deciding which of these drugs is responsible (blood tests, skin tests)?
     -I found that there are other drugs that can be used in place of metronidazole but what can be used in place of imodium? Both imodium and lomotil are piperidine opioids (found it on the internet) so is cross-allergy likely?
     - Are all opioid pain relievers and anesthetic agents to be avoided? My dog is von Willebrands affected so I never use peptobismol.

I am driving myself noodles anticipating the bleakest of possibilities. I will be grateful for any help you can offer.Regina

A: Regina- The only way that I know of to test to see which medication your Doberman is sensitive to would be to administer one of them and see what happens. If there was no reaction then the other medication would be the most likely culprit or it may take the combination of medications to cause the observed effect. Personally, unless I had to use one or the other of these medications I would be reluctant to test for a reaction in this manner.

I would be most suspicious of the metronidazole with this reaction, only because we have seen some odd adverse reactions to metronidazole and I can't remember a reaction to loperamide (Immodium AD (TM)). If loperamide is the culprit then diphenoxylate (Lomotil Rx) is very likely to cause reactions as well, as you have surmised.

It would be inconvenient not to be able to use loperamide or diphenoxylate but I can't think of a situation in which not having them would be life-threatening. It is possible to manage patients with diarrhea without using medications to control the diarrhea itself. Most of the time if the underlying cause of the diarrhea is controlled, hydration is maintained and there is good nursing care diarrhea will resolve whether medications are used to stop it or not.

Metronidazole is useful and it would be inconvenient not to be able to use it but everything it does can be accomplished with other medications. Fenbendazole (Panacur Rx) is supposed to be capable of killing giardia and many vets think that is safer to use than metronidazole.

I don't see any reason to avoid most anesthetics even if the reaction is to the loperamide. It would just be a good idea to avoid opiod narcotics as pre-medications or as pain relief medications before or after surgery. There are lots of possible anesthetic combinations and pain relief formulations available that do not rely on administration of opiods.

Hope this helps some. For right now, it seems logical to treat the giardia with alternative medications and hope that it isn't necessary to use either metronidazole or loperamide in the future. If the time comes when one or the other really seems necessary, remind your vet of the reaction and makes sure that a plan is in place to deal with any severe allergic reactions that may occur.

Mike Richards, DVM



Coughing Due to Allergies?

Q: Me again, the pest with the Vizsla (Oliver) with psuedomonas! I am still frustrated and scared. Oliver completed two weeks on Baytril. He was given the Baytril when he contracted kennel cough. We decided to treat him with the Baytril in hopes that it would kill any psuedomonas that might remain as well as to treat the kennel cough. He got kennel cough approximately 6 weeks ago and finished the Baytril about 4 weeks ago. He is still coughing!!!! The vet could not trigger the cough yesterday. I do not know what to do.

Oliver has allergies (dust, ragweed, grass etc....), is it possible for a dog that sneezes alot, probably due to allergies, to also cough as a result of the allergies? Can a dog become almost asthmatic (sp?)? I am taking him back to the specialist next week who will likely want to perform another endoscope into his lungs. They believe his psuedomonas is gone based on the sound of his lungs and x-rays, I do not believe this because they were always o.k. His breathing is not labored, he is eating is alert and very active (we now have another 22 mo. old Vizsla in our family which keeps him on the run).

I realize my messages are hard for you to respond to because he is not your patient but I look to you for some comfort. My main question today is whether coughing can be due to allergies. Thanks, again!!!

A: Suzanne-

Allergic bronchitis does occur in dogs. I have a cocker spaniel patient with this problem. He has to be treated with antibiotics several times a year and stays on either antihistamines or prednisone the rest of the time, depending on how bad the symptoms are at the time. It is difficult to treat him because it is always hard to decide if he is having a bad day due to the allergies or if he has a new infection. Consequently, he has had a couple of endoscopic exams and tracheal wash procedures as well as several sets of X-rays. We just keep working with his owner to keep tabs on him so that if we do choose the wrong path in treating him we are able to correct it quickly.

It would be good to discuss this possibility with the specialist or your vet. Good luck with all of this.
Mike Richards, DVM



Chewing on Feet- Allergies or Mange?

Q: Dr. Mike, In searching your archieves I have not found my problem. I have a two year old, Old English sheepdog that is chewing the hair from in between his back legs and his toes. There are no sores, redness or anything. It's like someone took clippers to his legs. this all of a sudden started. I have tried busying him with chew bones, etc. and he seems to do it at night when he's bored, I think. I have looked into allergies and am putting him on a allergy dog food. I was wondering if you have ever heard of this and if you have any advice. I have been a breeder for many years and never encountered this. Barb

A: Barb- I think the most common cause of chewing on the feet has to be allergies, at least in my area. This can occur with food allergies and with inhalant allergies (atopy). Once in a while demodectic mange is confined to the feet and it is always worth checking for this when there is hairloss. Immune mediated diseases like lupus and phemphigus can be involved in hairloss and irritation of the feet but usually some other area of the body like the ears, eyes, nose or lips is affected as well. If a food allergy trial diet is not beneficial consider testing for inhalant allergies. If your vet doesn't do this, he or she can refer you to a veterinary dermatologist. Since this is a young dog it seems best to have a diagnosis if at all possible so that a good treatment plan can be worked out -- especially since many of these problems will require lifelong control measures.
Mike Richards, DVM



RAST Testing

Q: Dear Vets, I would like to hear opinions on RAST testing. My 3 yr. old Mini Sch. started itching at 18 mos. (6 mos. after we got her) although we hadn't changed anything. It came on pretty suddenly, pawing mostly at her chin and ears. We did the RAST test and they said ALLIE was the most allergic dog they had ever tested and gave us only two dry food choices: venison/potato and duck/potato special ordered from IVD in CA. We tried duck first but she got too porky looking so we switched her to venison/potato. Her wt. was perfect and she loved it. She quit itching for quite a few mos. until summer came, then she started up again. The vet thought it was the grass so we maintained her on 2 1/2 mg. prednisone every other day which controlled the itch through the summer. We did that till long after the snow came and then tried to wean her off unsuccessfully. Since we hadn't had grass in mos., I no longer believed the grass was the problem.

We re-RAST tested her and this time the venison was "borderline" so back to duck/potato. I had to cut her food way down to control her wt. but ultimately, it's unchanged and I still can't get her off the prednisone or she starts itching immediately. How valid is RAST testing and what do I do next? Dianne

A: Diane- I am under the impression that the correlation between RAST testing and food trials to determine food allergy is very poor --- meaning that RAST testing is probably unreliable as a test for food allergies. A dog which is on a diet designed to eliminate food allergy problems who is still itching probably does not have food allergies. The exception is a dog that has food allergies AND other allergies -- in this case the dietary changes may be helpful in limiting the overall itchiness.

The correlation between RAST testing and skin testing for inhalant allergies is closer and RAST testing may be a reasonable alternative in this case when skin testing isn't available or isn't practical for some reason. Even so, skin testing is still the most reliable method of determining inhalant allergies. If there is a choice in testing method, it is probably best to use skin testing.

It is not unusual for allergies to start out as a seasonal problem and then become an all year disorder as the dog "learns" to be allergic to more and more things.

Anything you can do to control itching from any other source, such as fleas, mosquitos, heat, etc. will help limit the damage your dog does to herself.

Hope this helps answer your questions.
Mike Richards, DVM



Inhalant Allergies Masked As Grass Allergies

Q: I have a 2 year old english setter, hunting not show, that seems to have grass allergies. Last year, he developed a scratching problem on his belly causing his hair to thin. This occurs mainly during the spring/summer months and ends in fall. This year, I have not run him in the fields and he has not developed this problem. His litter mate didn't have the problem last year, but this year is hairless on his chest. He is run weekly in grass fields. I was just wondering what you thought.

Now, I have read some of the other replys regarding ear care and have a question of my own. My setter's ears are bothering him...scratching, shaking head etc. His ears have a dark, brown, waxy substance that builds up very quickly. I have heard that this is the residue left by mites, but others have said that it is a sign of a deeper ear infection. Please respond ASAP as hunting season is coming up and I need my friend in good health. Thanks, DAVE

A: Dave- Most allergies that appear to be grass allergies are actually inhalant allergies to various pollens --- which can include grass pollens. The pollens collect on the grass and dogs that are sensitive to them get exposed to high concentrations running through the grass. Allergies most commonly cause skin itchiness in dogs and that is the symptom you see. If keeping him out of the grass during allergy season works, that is great. If it doesn't you may need to use medications or consider hyposensitization to whatever he is allergic to. A veterinary dermatologist can usually do skin testing and prepare the allergy injections for you. Some general practitioners do this as well. It is not unusual for allergies to follow family lines and it does not surprise me that his brother has problems. Springers in my area seem very prone to allergies.

The ear problem you are seeing is probably also due to allergies, although ear mites or ear infection for other reasons is possible. Chronic ear infections are commonly caused by inhalant allergies (atopy). I am pretty sure that this is the most common cause of persistent ear infections in dogs. It is important to control these ear infections early and consistently. If this is not done the inflammation changes the structure of the ear canal and makes it harder to treat the infection and in many cases more difficult bacteria to kill eventually come to inhabit the ear. Please take your dog to your vet and find out if this is the problem and work with your vet to develop a plan to control this problem consistently. Not only is it the right thing to do just to keep him comfortable, he'll hunt a lot better if his ears don't bother him, probably.
Mike Richards, DVM



Antihistamine Dosage

Q: my dog has grass allergy.I try your recommend treatment of giving my dog 4mg chlorphenirmine . however, I have been giving one pill when everytime she starts to itch again. however, I was wondering - I like to start properly treatment cycle so , how often should you give a 6lbs dog one of these 4mg pills?????

A: I'd probably try 1/2 of a pill two or three times a day in a dog this size ( 6 lbs.) It does help to use this on a continuous basis during the allergy season. Remember that antihistamines do not work for all dogs -- only about 10 to 20% of them. When it does work it is awfully convenient, though.

Good flea control is always helpful. The new flea products Frontline (Rx), Advantage (Rx) and Program (Rx) are all helpful in eliminating fleas as a contributing factor in itchy skin diseases.
Mike Richards, DVM



Swollen Lymph Nodes

Q: Dr. Mike: Over the past three months I've noticed that my 10 yr old Shih's lymph nodes began to swell. Only other behavior difference is an increased appetite. Did take her to vet and had largest lymph note removed and sent to Cornell for evaluation. Reports states that they were unable to determine cause. May be precancerous or an infection. She was put on antibiotic for several weeks with no effect. Next came predisone and still no effect. Vet would like to remove another lymph node and retest. Should other testing be performed prior to another removal? Could there be another cause? Thank you for help.

A: There are few things more frustrating than swollen lymph nodes and a non-specific pathology report on them. It is unfortunate, but lymph nodes enlarge for a lot of reasons. It is always a good idea to carefully repeat the physical exam, looking for new clues as to what is going on. Sometimes, a general lab panel, X-rays or bacterial cultures can be helpful in finding the cause of the lymph node enlargement. We see this pretty frequently in our practice secondary to allergies. I am not sure if the lymph nodes enlarge as a direct result of the allergy or because secondary skin infections are common with allergies -- but they are frequently enlarged in dogs with chronic allergy problems. The most serious concern is lymphoma (cancer of the lymph nodes). Removal of the node is helpful in diagnosing this, obviously.

An intermediate step prior to removal of another node might be to aspirate several of the lymph nodes and send smears of the aspirates to the pathologist. We do this before removing lymph nodes in many cases and often the diagnosis can be made from the aspirate.

Another consideration is referral of the whole dog to the veterinary school. They have lots of specialists in different fields and can often figure out problems that elude general practitioners like myself.

Good luck with this.
Mike Richards, DVM



Reaction to Wasp Sting

Q: Hi, I have a five year old English Springer spaniel bitch "Toto". Eighteen months ago Toto was stung by a swarm of wasps literally being covered from her nose to her tail in wasps. A visit to the vet and a dose of hydrocortisone calmed me down! Toto, didn't seem to mind the experience. A week later Toto developed a petechia type rash, around her gums, on her abdomen and around her vulva. She also appeared to be menstruating yet was not due to come on heat for about three months. The vet was most alarmed initially suspecting poisoning which was causing a clotting/bleeding disorder. Her blood film revealed one very anemic dog with a very low platelet count. The vet suggested that it was probably an auto immune disorder, the cause of which could not be determined. Toto responded very well to corticosteroids being on them for some four months.(She became huge!) She has since not had any further problems. The vet suggested that she not be allowed to have pups. Is it possible that the original episode of the wasps strings could have provided the trigger to her illness? I would (and so would the vet)be interested to hear your views.

A: Insect stings have been reported to cause delayed hypersensitivity reactions in some dogs. These reactions occur five or more days after the sting(s). They can have varied signs, including wheal formation, lamenesskidney failure, bleeding disorders (including platelet destruction), vomiting or diarrhea. I can not remember exactly where I saw these references but I think it was in one of the Kirk's Current Therapy books. It is possible that immune mediated thrombocytopenia (IMT) may also occur as a result of bee stings but I don't think I have seen a reference to this. Corticosteroid use in the delayed hypersensitivity reactions is usually only necessary for short periods but in IMT it is generally recommended to continue their use for several months and then to withdraw them slowly. I think you should discuss withdrawing the corticosteroids with your vet. Obviously, you want to do this carefully, just in case the symptoms return. If withdrawal of the medications is successful, you still have to watch for bee sting signs since they could return if that was the original cause of problems. Remember, I can't see or evaluate your dog -- so your vet's opinion is worth a lot more than mine!
Mike Richards, DVM



Atopy in Staffy

Q: Dear Dr.Mike, I have a pure bred red male staffy who is 2 years old. Last year in January he started biting his paws and got a bad rash on his chest and under his armpits also his ears were red and hot. This January it happened again. I have been told by two vets that it is atopy and he has had Delta-cortef and Prednil. I am distressed that he has this as we were hoping to bred from him as he has excellent lines (U.K). Will this get worse and will his quality of life be changed? I have noticed it is worse when we are in the garden and he plays on the grass. I have started to spray daily for fleas(there have been none visible) and mosquitoes to see if this is pushing him above his threshold, then we will start on allergy tests. Is this a breeding fault? I would like to know because I will contact the breeder as it is distressing to see our much loved dog itching himself raw to a painful point and knowing he has to take steroids or cortizone. I eagerly wait for your reply. Regards

A: It is not unusual for dogs with atopy to seem to be much worse after being out on grass, especially if it is wet. I think this is because the pollens naturally land on the grass and when it is wet, it is easier for them to stick to the dog's skin or even penetrate it. Here, in Virginia, January wouldn't be the typical season for atopy but I suppose that isn't the case where you are (Australia?)!

I am not sure if you have access to lufenuron (Program Rx, from Novartis), imidacloprid (Advantage Rx, Bayer) or fipronil (Frontline Rx, TopSpot RX, Rhone Merieux), these products seem to help more than anything else we have tried for flea control. Lufenuron is most effective in our practice in dogs and cats who are confined in some manner and not out playing a lot with other dogs, cats, etc. It is an oral product that prevents flea reproduction. The other products seem to do better for pets who are less likely to be confined and may be better for pets with flea allergy since they kill adult fleas. Having a highly allergic dog, I use both the lufenuron and fipronil for my pets.

Atopy is sometimes controllable using a combination of essential fatty acid supplementation (DermCaps Rx, EFA-Z Rx, OmegaDerm Rx, you get the idea ...) and an antihistamine like atarax, diphenhydramine or chlorpheniramine, you get the idea again.... This combination only works in about 10 to 15% of dogs but when it does work it is nice because there are far fewer side effects that with the use of corticosteroids.

I personally consider severe allergic disease to be a reason not to breed a dog since we really do seem to see this in family lines of affected dogs. The other traits of the dog would have to be very very good to offset that tendency since it makes the dogs so uncomfortable and is often a lifelong illness. Since this is an important decision it seems worthwhile to confirm the atopy through testing as you indicate you intend to do.

Good luck with this -- I hope you find a more treatable condition is present with further testing.
Mike Richards, DVM



More Allergy Development As Dog Gets Older?

Q: Dr. Mike, I have a 1 year old Shetland Sheepdog that has been diagnosed with food(eggs, milk etc..) and inhalant allergies(dandelion,dust mites,juniper,etc..). My vet has started her on a special food and will evaluate her at a month. My question is are these common in Shetland Sheepdogs and because she is so young what is the probability that she will develop more allergies?

A: Shetland Sheepdogs are not listed as especially prone to atopy in either of the dermatology texts I have at home. We see several shelties with flea allergy in our practice but where we live, flea allergy is so common that there probably aren't any breeds that live in our area that aren't represented in among our flea allergy patients.

Dogs with atopy tend to become allergic to more things as they get older, based on lengthening of the "allergy season" with age, seen in dogs with this problem in our practice. I do not know if early use of immunotherapy (antigen injections or "allergy shots") is helpful in stopping this trend.

I would be very reluctant to believe food allergy test results from allergy testing done on blood samples. Most of the references I see to this testing indicate it is not very reliable for food allergies. It is more reliable for inhalant allergies but not as good as skin testing. The food trial is a good idea. Using diets composed of ingredients your dog has never eaten, it is possible at times to determine what foods they are allergic to and to plan a diet that won't cause itching. If that is the only problem, the condition is controllable with dietary changes alone. While that is rare, it is worth looking into when facing a possible lifelong problem. Good luck with this.
Mike Richards, DVM



Infrequent Plant Allergy- Vet Needed?

Q: Dear Doctor Mike. My Jack Russell is allergic to Wandering Jew. My yard is clear of the plant but on two occasions she has come into contact with it during a walk. Is it necessary to visit a Vet each time for a steroid shot and antibiotics or will the condition safely clear up with home treatment and avoidance? The symptoms are limited to a rash on her underbelly and armpits and doesn't seem to cause her any distress at all.

A: The problem doesn't sound too serious and it seems to me that avoidance of the plant and perhaps topical treatment with corticosteroid ointment in the affected areas might be enough to treat it but I really think that you should also discuss this with your vet who has seen the severity of the lesions caused by the allergy.
Mike Richards, DVM


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...