Antihistamines for Pets' Allergy Problems

Sometimes, your pets allergy problems require medication to alleviate the symptoms. One of the most common types of medication that your veterinarian may prescribe is an antihistamine. Let’s look at how antihistamines help relieve allergy symptoms and what some of the most common antihistamines are. We’ll also examine common side effects so you’ll be able to make an informed decision about adding these medications to your pet’s allergy control regimen.

How Antihistamines Help Control Allergy Symptoms

At their most basic, antihistamines control histamine, which is a chemical an allergic animal’s immune system produces in response to a perceived threat from an allergen, such as:

  • a food ingredient
  • flea saliva
  • pollen
  • dust mites
  • other irritants

Histamine causes the animal’s skin to flush and itch, and hives to form. Some allergic pets also have problems with their digestive systems, such as vomiting or diarrhea, as a result of histamine being released into their bodies. In more extreme allergic reactions, your pet may develop breathing problems or begin choking as a result of the histamine being formed in by his immune system.

Antihistamines help clear up reddened skin, reduce itching and hives, and they can also help ease breathing problems caused by histamine-congested airways.

The Most Common Antihistamines for Pets

Your veterinarian will select an antihistamine for your pet based on his or her breed, weight and allergy type. Potential side effects, which we’ll discuss shortly, will also be evaluated before medications are prescribed, and any other medications your pet takes regularly will also be considered when making an antihistamine selection.

  • Chlorpheniramine, or Chlor-Trimeton, is used to treat skin problems associated with allergies in dogs and cats. It is not recommended for pregnant animals or those pets with high blood pressure, overactive thyroid, prostate problems, intestinal or urinary blockages.
  • Clemastine fumarate, best known as the brand name Tavist, is a long-acting antihistamine that can treat atopic allergies in cats and dogs. The main benefit of this medication is that it requires fewer daily doses to be effective than other antihistamines. It is not recommended for pets with glaucoma, severe heart disease, prostate enlargement, or urinary or intestinal blockage.
  • Cyproheptadine, or Periactin, is used to treat a variety of atopic allergy symptoms in both cats and dogs. It is also used to treat feline asthma and can be used to stimulate the appetites of cats that do not readily eat. It is not recommended for use in pets with glaucoma, severe heart disease, liver disease, kidney disease, prostate enlargement, or with urinary or intestinal obstructions.
  • Diphenhydramine, also known as Benadryl, is safe for use in both dogs and cats. It is most often used to control flea allergies, atopic allergies or allergic reactions to insect bites and stings. It is not recommended for pets with prostate problems, heart disease, an overactive thyroid or glaucoma.
  • Hydroxyzine, most commonly known by the brand name Atarax, helps control atopic allergy symptoms in cats and dogs. It is not recommended for pets with glaucoma, heart disease, overactive thyroid, prostate enlargement or with intestinal or urinary blockage.

Potential Side Effects of Antihistamines

Although each antihistamine has unique side effects, there are some general side effects to this class of drug, including drowsiness, appetite loss or stomach upset. Ask your veterinarian to carefully explain side effects to you before you leave the clinic so you’ll know what side effects may pop up and which ones are potentially serious.