Does Your Pet Have Allergies?
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By Kim Thornton Is your dog or cat scratching uncontrollably? If so, your pet might have allergies. It’s unclear how many pets are affected by allergies, but veterinary dermatologists agree that itchy skin is a common symptom.  There are three main types of triggers for allergic reactions: flea bites; pollens, molds, grasses, trees, weeds, dust and dust mites; or certain food ingredients. Unless it’s clear from an examination or history what’s causing the itchiness — the presence of flea dirt, for instance — diagnosing allergies is a process of elimination. Veterinarians may tighten up flea control, do skin scrapings to check for infections caused by bacteria or yeast (common in allergic cats and dogs) or start the pet on an elimination diet to rule out food allergies. “If everything goes away, we’ll slowly stop doing one thing at a time and learn which of our allergies was the biggest player. If all the itching doesn’t go away, we’ve by default made the diagnosis of a pollen or mold allergy because that’s the allergy we really can’t control or avoid,” says Catherine Outerbridge, assistant professor of clinical dermatology at the University of California School of Veterinary Medicine in Davis. Flea allergies When fleas bite pets, some of their saliva is injected into the animal’s bloodstream, sometimes causing an allergic reaction. Some pets are exquisitely sensitive to flea saliva, and the bite of a single flea can send them into a frenzy of scratching. Others need much more exposure to flea saliva before they have a reaction. In dogs, the main sign of flea allergy dermatitis, or FAD, as it’s known, is itchiness on the back half or third of the body. Cats have a different reaction pattern, usually little crusts or sores along the back and up toward the shoulders, although some of them are also itchy on the back half of the body. Flea infestations are less common these days because of the widespread use of topical spot-on flea control products. How well they work depends on how often they’re applied, the number of fleas in the environment and how often the pet gets wet. “It may be that the animal has hot points in the environment where it really comes into contact with a lot of fleas and the topical products for that sensitive animal are not killing fleas quickly enough to prevent exposure to flea saliva and triggering a reaction,” Dr. Outerbridge says. Water-loving dogs who spend every day in the pool or lake also may have poor results with spot-on treatments, even those that are water-resistant. In those cases, veterinarians may recommend a faster-killing daily or monthly pill. And remember, before using any flea-control product on your cat, read labels carefully. Just because something can be used safely on dogs doesn’t mean it is safe for cats. Food allergies It’s unclear why some pets develop allergies to certain foods, usually common animal or plant proteins such as beef, chicken or soy. An elimination diet — trial-feeding a food that contains only ingredients the pet has never eaten before — can help determine if a food allergy is the cause of a pet’s itching and scratching. Because most commercial pet foods use the same ingredients, switching from one brand to another won’t help. The animal must eat a food containing novel proteins — such as kangaroo and oats or fish and potatoes. Lamb and rice diets have a reputation for being hypoallergenic, but that’s not true. If the signs go away after eight to 12 weeks of feeding the hypoallergenic diet exclusively, ingredients are added back into the diet one by one until it becomes clear which food is causing the problem.
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