In part one of this comment we talked about what flea, atopic or inhalant and contact allergies are and how they are affecting our pets. Today’s conclusion deals with the 4th type of allergies common in pets: Food allergies. Plus we will address allergy testing and some of the treatments available.
Food allergies are not related to a season, while many atopic allergies start out as a seasonal problem, says Daniel O. Morris, D.V.M., a board certified veterinary dermatologist and chief of staff of the veterinary hospital at the University of Pennsylvania in Philadelphia. Dogs and cats that develop atopic allergies usually show symptoms between 1 and 5 years of age, he says, but food allergies can crop up at any time. They are high on the list of suspects when a dog or cat first exhibits itchy skin at an age less than 6 months or over 5 years.
To test for food allergies, the pet is put on an "elimination diet" for at least 10 weeks, which means it is fed food that consists of a protein and carbohydrate that the pet has not eaten before, such as duck, venison, and potatoes. These special foods may be found in specialty retail stores. Or the owner may choose to feed the pet a homemade diet of foods recommended by the vet.
If the animal's itching subsides by at least half, the allergen is considered to be one or more food ingredients, says James Jeffers, V.M.D., a board certified veterinary dermatologist at the Animal Allergy and Dermatology Clinic in Gaithersburg, MD. To confirm this, the owner can reintroduce the old food to see if the symptoms return. To find the specific ingredients that trigger the allergy, the owner should feed the special diet again and add one ingredient at a time from the old diet for at least a week until the itching increases, indicating that the last added ingredient is an allergen. Or the owner may choose to stay with the special food to avoid causing the pet discomfort each time an allergic ingredient is fed.
While the pet is being tested for food allergies, it should not be given treats, chewable medications, table scraps, or rawhide toys that may contain an allergen.
To check for atopic and contact allergies, veterinary dermatologists use an intra dermal allergy test, or skin reaction test. The pet is mildly sedated, a postcard sized area on the side of the pet is shaved, and small amounts of potential allergens are injected into the skin on the shaved area. If the pet is allergic to a particular substance, the skin will become inflamed at the area of the injection.
Jeffers tested Nora, a wire fox terrier, for 58 different allergens. The dog had been "scratching and biting herself all over, 24 hours a day," since it was 3 months old, says owner Katie Mathews of Bethesda, Md. "The scratching kept Nora up all night and kept the family up all night," she says. Before she was referred to Jeffers, Mathews had taken Nora to several veterinarians, who prescribed various antihistamines, shampoos, sprays, and a food elimination diet, none of which worked. "Steroids were successful," says Mathews, "but I didn't want to keep her on them because of the long term side effects." Mathews also "wanted to get to the root of the problem" so that the allergic substances could be avoided if possible.
Through skin testing, Jeffers determined that Nora had atopic and contact allergies and was allergic to dozens of substances, including pollens, molds, dust mites, grass, cotton, and wool.
Although allergies can't be cured, they can be controlled by avoiding the allergens, treating the symptoms, or desensitizing the pet. In Nora's case, all three methods are used.
Fleas, food ingredients, and some substances that trigger contact allergies may be avoidable, but "with atopic allergies, avoidance is virtually impossible," says Jeffers.
Drug products are available to relieve the symptoms of itchiness and inflammation in pets. Like any drugs designed for animals, these products must obtain FDA approval before they can be marketed by meeting rigorous scientific standards similar to those for human drugs.
The FDA approved two itch-relieving drugs in 2003: Atopica (cyclosporine) for controlling atopic dermatitis in dogs weighing at least four pounds, and Genesis Topical Spray (triamcinolone) for controlling itching related to allergic dermatitis in dogs. Atopica, a product of Novartis Animal Health US Inc. of Greensboro, N.C., is a capsule given orally. It works by inhibiting specific immune cells from reacting to allergens, and can be given as a lifelong treatment. Genesis, made by RMS Laboratories Inc. of Vidalia, Ga., is a steroid spray that is applied to a dog's skin for up to 28 days. Both of these drugs must be prescribed by a veterinarian.
The FDA has approved other steroid products for short term use in dogs and cats to relieve inflammation and itching. Long term steroid use is discouraged because these drugs work by suppressing the immune system; this suppressant action over time can leave an animal vulnerable to infection, diabetes, and other conditions.
Veterinarians often prescribe anti histamines approved by the FDA for humans to relieve itchiness in pets. Under the Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA), veterinarians may legally treat dogs and cats with drugs that have been approved for people but not for animals. Pet owners should check with their veterinarians before giving a pet any human medications, including over the counter antihistamines.
"If we can control the allergies through medication for occasional flare ups, antihistamines and steroids are useful," says Troutman. But if these medications are needed continuously to provide relief, Troutman recommends seeking other options, such as immunotherapy.
Immunotherapy is a treatment that stimulates the immune system to decrease the body's reaction to allergens. Similar to people with allergies, animals can be given immunotherapy, or desensitization injections. These "allergy shots" contain small amounts, or extracts, of the substances that the animal is allergic to, based on the results of skin testing. The owner gives the shots to the pet at home, usually in the scruff of the neck. The extracts used for allergy testing and treatment in veterinary practices are licensed by the U.S. Department of Agriculture's Center for Veterinary Biologics.
Somewhere between 50 percent and 70 percent of dogs and 75 percent to 80 percent of cats respond to immunotherapy, depending upon the study reported, says Morris. "Occasionally, it is so effective that the animal is normal without other treatments," he says, but the majority require medications in addition to the injections. The injections are usually given every 7 to 21 days, depending on the pet's response, says Morris. And rarely does an animal become permanently desensitized so that the injections can be stopped.
Nora gets a weekly injection. Mathews also gives her Atopica and, when the pollen count is up, an over-the-counter antihistamine. Mathews has placed synthetic blankets around the house for Nora to lie on, since the dog is allergic to cotton and wool in the furniture and carpeting. Nora also has a vinyl bed to lie on in the yard, since she's allergic to grass. This allergy management program helps keep the 18-month-old dog comfortable. "She still has periods of scratching," says Mathews, but "she's not biting herself as much and she's sleeping at night." Mathews reports that her other dog, Nora's littermate Nick, is allergy free.
Allergies in pets are neither preventable nor foreseeable, says Morris. "You can have one puppy out of a litter of 10 with allergic skin disease, or it can skip generations. We can't possibly predict it," he says, even if you have a pet examined by a vet at a very young age.”
This comment was written with information obtained in the FDA Consumer Consumer Magazine.
Pet itching for relief? Leading cause Allergies Part 1 Introduction, Flea, atopic (inhalant) and contact allergies