Antihistamines for Dogs
This page looks at antihistamines for dogs - antihistamines such as Benadryl are often used as dog allergy medication to relieve
symptoms such as itchiness. How exactly do antihistamines work? Are there any side-effects? Read on and find out.
Besides corticosteroids, antihistamines are another type of dog allergy medication frequently used by veterinarians to relieve the itchiness in the allergic dog.
How Do Antihistamines Work?
As mentioned in our page on Common Dog Allergies, histamine is a chemical released
by mast cells in an allergic dog's body in response to an exposure to allergens such as pollens, mold, house dust mites, etc. The released histamine locks onto
histamine receptors (called H1 receptors) which are located on various cells in the dog's body. When that happens, the cells undergo biochemical changes and produce
allergy symptoms such as itching, runny eyes and runny nose. Histamine receptors also release other chemicals that increase inflammation, resulting in inflammation of
the skin in the allergic dog.
Antihistamines work by physically preventing (blocking) histamine from connecting with its histamine receptor, thus preventing the biochemical changes which produce the
allergy symptoms.
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How Effective Are Antihistamines for Dogs?
Various studies on the effectiveness of antihistamines on dogs have been conducted with variable results. Specifically, about 10 to 30 percent of dogs have been found to
show improvement after using antihistamines for their allergies.
Compared with corticosteroids, antihistamines are not as effective because antihistamines block only the histamine receptors on cells in the body. However,
histamine is not the only chemical released by the mast cells. Other chemicals released can also cause allergy symptoms such as itching.
In addition, antihistamines for dogs work best when taken before allergy symptoms are evident - they are not so effective if taken when the allergic dog is already
showing signs such as severe itching.
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What Are Some Common Antihistamines for Dogs?
Some common antihistamines for dogs include:
- Benadryl (diphenhydramine)
- Atarax/Vistaryl (hydroxyzine)
- Chlortrimeton (chlorpheniramine)
- Tavist (clemastine)
- Periactin (cyproheptadine)
- Temaril (trimeprazine)
Different dogs react to antihistamines differently. If you are lucky, you may get an antihistamine that works for your dog first time round. On the other hand, there is
also a possibility that none of the antihistamines work! Only by trial and error can we determine which antihistamine works best for our dog.
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What Are Some Possible Side Effects of Antihistamines on Dogs?
Antihistamines seem relatively safe to be used to treat dog allergies. The one major side effect is sedation - your dog may be sleepy when taking this medication. In some
cases, sedation wears off in a few days.
Dogs with liver disease should use antihistamines with caution since antihistamines are metabolized by the liver.
As well, dogs with the following conditions should not use antihistamines:
- Glaucoma
- Urinary retention disorders
- Pregnancy
Related Topics
Common Dog Allergies
Canine Atopic Dermatitis
Flea Allergies in Dogs
Dog Food Allergies
How to Treat Dog Allergies
Prednisone for Dogs
Allergy Shots for Dogs
Natural Allergy Relief for Dogs
References
Messonnier, S., The Allergy Solution for Dogs (Three Rivers Press, 2000).
Mar Vista Animal Medical Center (http://marvistavet.com/index.html)
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