Atopy – Allergic Environmental and Inhalant Dermatitis Dermatology for the Itchy Pet Parents General Information Canine atopic dermatitis is a complex environmental and inherited tendency to display allergic symptoms like scratching, chewing and rubbing at the face, paws, armpits, and stomach. The age at which this is first seen can be as young as three months or as old as seven years, but the average is between one and three years of age. Common causes of atopic dermatitis include molds, dust mites, pollens (from trees, weeds and grasses), feathers and dander from other animal species. These microscopic particles can set up an allergic skin reaction in a sensitive individual (both humans and pets!). Depending on the particular allergy the symptoms may be mild initially and seasonal (ie- pollens) or year round (ie- house dust mites). With time, the immune system of the individual becomes increasingly sensitized and reactive, and these signs become more severe and continue for a longer period. Allergic signs can be aggravated by concurrent flea infestation. An animal that is allergic to pollens can also be allergic to insect bites. Even if there are no fleas or other insects seen, a single bite can aggravate the dermatitis, and cause generalized dermatitis signs for 2 weeks!. What are the signs of atopy? The major signs are itching and scratching, causing self trauma and hair loss, often in the armpits and the groin. Dogs also rub their faces and lick their feet. However this is not specific for atopy, as both food, mange mites, and insect bite allergies can produce these signs. The other signs which result from allergic scratching include hair loss, redness, scale formation (large patches of flaking dandruff), a darkening of the skin color, and a bad odor. How do we diagnose atopy? There are several options to identify a specific environmental/inhalant allergy. A dermatologist specialist can perform a skin test in the hospital which involves clipping the side of the chest and pricking the skin with tiny amounts of a large series of purified allergen extracts. Reactions to each of the extracts (swelling, hives, wheals, and redness) are observed over the next thirty minutes. The other option is a blood test, which takes just a minute to draw. New advances allow veterinarians to send a blood serum sample from a pet to one of a few specialized veterinary laboratories in the USA and Canada, where they are analyzed for an extensive range of allergens, including region-specific allergens common to your area. However, the tests are affected by a number of drugs including antihistamines and corticosteroids. In some cases, we may have to wait one or two months after the last drug administration until we are able to perform accurate allergy testing. The tests are not affected by antibiotics.
Treatment The preferred method of treatment is to hyposensitize the pet patient using an allergy vaccine which is made up specifically for that individual patient (also how humans are effectively treated for these types of allergies!). For the first 4 weeks the animal will receive injections (allergy shots) every other day. Thereafter, an injection is given weekly. After your pet is in remission, then time between treatments is tapered further. Owners are encouraged to administer the shots at home; the injections are tiny, and usually in an insulin syringe. In case of a mild seasonal allergy of less than two months, antihistamines and a short tapering course of corticosteroids (which relieve the symptoms of the allergy) may be the treatment of choice. Known common side effects of corticosteroids include increased thirst, appetite, weight gain, and frequent urination. If given for an extended period of time, corticosteroids may cause increased susceptibility to infection, hair loss, liver damage, muscle weakness, diabetes mellitus, vomiting and/or diarrhea. Long term corticosteroid usage is therefore not recommended for young dogs. In the older dog, corticosteroid therapy at low doses on alternate days may be considered as a treatment if necessary. The most common side effect of antihistamines is sedation, also noticed in people as drowsiness. Although these are relatively safe medications, they are unfortunately not as effective in dogs and cats as they are in humans. Some examples are Benedryl (diphenhydramine HCl), cetirizine, loratidine, and chlorphenaramine. It may require trial and error to see which is effective for each individual. Even if not completely effective, they can be used to safely decrease the amount of steroids to be given. A newer drug treatment for atopy is called Atopica. This is a brand name for cyclosporine, an immune system suppressant drug that ‘dampens’ or tones down the pet’s “immune alarm system” that goes off in response to contacting an allergen. In a medical nutshell, cyclosporine induces reversible immunosuppression by inhibiting the initial antigen triggered activation phase of CD4+ T lymphocytes. It is very effective for many patients, but requires strict monitoring with a veterinarian and periodic blood tests, at six weeks, then six months apart. There are potential side effects that may require a dose adjustment, and food cannot be offered for two hours before or after treatment. Natural Complementary Therapies There are a number of holistic and herbal based therapies and nutraceuticals that may help significantly with allergic pets. These safe complementary and alternative ideas can help to lower medication dosage needs and create a positive balance for the immune system. We’ll discuss Omega-3 Fatty Acids, probiotics, Bioflavanoids, plant and herbal therapies, local honey supplementation, and topical treatments such as shampoos in the next column! Schedule an examination and allergy consultation for details and a personalized pet plan to safely decrease the itching!
