An allergy to an environmental substance is called atopy. Atopic cats and dogs usually have itchy paws, face, armpits and/or bellies.
Atopy is diagnosed by excluding all other causes of itch (see our Itchy Pet handout for an explanation of the various causes of itching). Most pets develop environmental allergies between the ages of 2 and 5. Common environmental pet allergens include grasses, weeds, trees, molds, dander, insect feces, and house/storage mites. Allergy testing can determine which allergen your pet is allergic to, either with a blood test or by intradermal testing performed by a veterinary dermatologist.
So how do these allergens cause your pet to itch? When the natural defense barrier of the skin is compromised, allergens gain contact to the immune system and prime it to react to the allergen in the future. When re-exposure occurs, the primed immune system releases substances called cytokines that cause itch and inflammation. Current therapies for atopic dogs are often multi-modal and are targeted at both strengthening the skin’s defenses, preventing release of the substances causing itch, and decreasing the immune system’s response to the allergen.
The skin has a lipid layer that acts as a natural defense to allergens. This lipid layer is much thinner in atopic pets. By improving this layer, pets with atopy have less contact between allergens and their immune system allowing fewer itch-causing substances to be released. Omega-3 fish oils and topical spot-on therapies help rebuild the skin’s lipid barrier. Hills’ diet, Derm Defense, also works to rebuild this barrier through its patented formula. In addition, decreasing the amount of contact the skin has with allergens helps decrease the allergic response. You can limit your pet’s exposure by wiping their paws/underside after being outside, use protective dog suits (K9TopCoat.com), use air purifiers/furnace filters, and use dust mite control products (ecologyworks.com). By restoring the skin’s natural defense and limiting the allergens contacting your pet’s skin, you can improve your pet’s allergies.
Treatment For Dog Allergies
There are multiple drug options available to block release of the substances that cause itching. Although widely available for people, antihistamines are often not helpful in pets because histamine is only minimally released in most pet’s allergic response. Cortisone (Prednisone, Temaril P) medications are relatively inexpensive and very effective at preventing release of the majority of inflammatory substances causing itch. Cortisone, unfortunately, has side-effects (excessive thirst/urination, hunger, panting and organ damage) and we therefore generally try to limit the duration of use of cortisone medications. Cyclosporine (Atopica) also effectively blocks these substances in most dogs and cats with much fewer side-effects, however, Atopica takes 4 to 6 weeks to be effective.
A newer medication, Apoquel, inhibits release of IL-31, a substance that sends the signal to the brain to feel itchy. Apoquel is for use in dogs only, and often results in the same control of the pet’s itching without the concern of side-effects as with cortisone. Another newer therapy for dogs, Cytopoint, is not a medication at all. Cytopoint is a monoclonal antibody treatment. These monoclonal antibodies stick to the immune cell where the allergen needs to attach, thus preventing the allergen from triggering that cell’s inflammatory response. Monoclonal antibodies are normally present in the body and therefore have no side-effects. Cytopoint injections typically are given monthly. Most atopic pets will need one of these treatments to block release of these itch-causing substances and make them more comfortable.
For pets with multi-season allergies, we may suggest immunotherapy. With immunotherapy, we teach the immune system to stop reacting to allergens by giving the pet small amounts of what they are allergic to. Over time, the immune system becomes desensitized to the allergen and there is less or no allergic response. First, we need to determine what allergens your pet reacts to in order to identify what allergens to include in their allergy serum. This serum is then either injected weekly (we can teach you how to do this at home) or squirted into the mouth twice daily. It can take up to 6 to 9 months to see improvement, with about 70% of pets responding. If the pet improves, injections can be given less frequently during non-allergic times of year. Oral therapy must continue twice daily year round. We generally recommend allergy testing if we feel the pet would benefit from desensitization therapy as the main reason to test is to determine what allergens to include in the allergy serum. Since treatment is needed long term, we generally reserve immunotherapy for pets whose allergies last many months each year and do not respond sufficiently to medications.
Although the allergic pet’s itching is often debilitating and recurrent, newer therapies have given us many options to effectively control the scratching and significantly improve your pet’s quality of life. Although we cannot “take the world away”, we can make your atopic pet happier and more comfortable.