Antihistamines for Eye Allergies in Dogs

Eye allergies in dogs can be distressing for both you and your pet. If your dog has discharge from the eyes or anything unusual in and around the eyes, you should conduct a vet check. It could be a simple eye allergy or something more serious, such as glaucoma.

Eye Allergies

Canine eye allergies are caused by an abnormality in the immune system, which generally develops when the pet's body reacts negatively to allergens in the environment or food. These allergens trigger an immune response, indicating that the dog is hypersensitive to the allergen. An element known as histamine is released by the body in response to the allergen, and this causes inflammation and irritation. One of the most common types of eye allergies observed in dogs is known as allergic conjunctivitis.

Causes of Canine Eye Allergies:

  • Dust
  • Pollen
  • Debris
  • Dairy products
  • Additives in food
  • Preservatives in food
  • Corn
  • Flea bites 
  • Insect bites

Symptoms of Canine Eye Allergies:

  • Swelling
  • Redness
  • Transparent tear discharge from the eyes
  • Irritation 
  • Mild pain


Canine eye allergies are generally treated with antihistamines, also known as anti-allergy drugs. Antihistamines work by blocking the effects of the histamine released during an allergic response. The antihistamines attach themselves to areas where histamines get attached, and this blocks the allergic response. However, they only mitigate the symptoms of the immune response and aren't a treatment for the eye allergy.

Antihistamines should be administered in addition to keeping the allergen or causative factors away from your pet. Besides administering antihistamines and removing allergens from your pet's environment and food, you should also wash his eyes regularly with an isotonic solution.

Treatment of Eye Allergies with Antihistamines

Antihistamines are generally used in the treatment of canine eye allergies. Even human antihistamines available over the counter, such as Benadryl, can be used to treat a pet with an eye allergy. The standard dosage of Benadryl is 1 mg for every pound of body weight. This dosage should be administered three times a day for two weeks. However, it's essential that the advice of a vet is sought before administering Benadryl, because some pets might require a lower dosage.

Side Effects of Antihistamines

The common side effects of most antihistamines and Benadryl in particular are drowsiness, vomiting, diarrhea, retention of urine and dry mouth. Antihistamines are contraindicated in pregnant or nursing dogs and pets with hypertension, prostate disease or urinary obstruction. They shouldn't be administered in conjunction with tranquillizers or barbiturates, and an overdose can cause extreme drowsiness, seizures, coma and even death.

Before treating your pet for eye allergies, it's advisable to confirm with a vet that the condition is indeed an eye allergy. Removal of the allergen from your pet's environment and food, administration of antihistamines in conjunction with antioxidants and Omega-3 fatty acids, and cleaning your pet's eyes regularly can all provide relief to your pet.