Allergies in Dogs and Cats


“My dog won’t stop scratching!” is one of the most common issues presented to veterinarians in our exam rooms. Ranging from “just a bit more itchy than normal” to “keeping me up at night due to constant itching”, we see it all. And the hardest part is that it can be VERY tricky to determine exactly what the underlying cause of that itch might be. One of the more common reasons (among many) for itching includes allergic disease, the topic of our discussion in this blog.

Allergic disease in dogs and cats often manifests itself as skin irritation, including ear infections/irritation as well. While humans may suffer from sneezing and watery eyes with allergies, dogs and cats more often may show signs including itching/scratching the body, ears, face; licking of the feet, legs, rear; rubbing of the face, ears, body on objects/floor; red/itchy eyes; or even vomiting/diarrhea (especially with food allergies). Allergies can start at any point in your pet’s life, but most commonly begin between 6 months and 5 years old. Dogs and cats can have one or multiple allergies, and allergies can be seasonal or non-seasonal depending on the underlying cause(s). The three most common types of allergies in dogs and cats include flea bite allergy, food allergy, and environmental allergies (atopy). One, two, or all three of these allergies could be working in combination to cause your pet to be uncomfortable. These allergies can also lead to vicious cycles of skin irritation and secondary skin infections.

Flea Bite Allergy (flea bite hypersensitivity, flea allergy dermatitis):

One common cause of itching is flea bite allergy. Pets that are allergic to fleas are actually allergic to the saliva produced by the flea. It can take as little as one or two flea bites to create a severe discomfort in a pet. Therefore, the pet only needs to be exposed to one flea to be affected. A pet that becomes allergic to flea bites are often most itchy in what we call the “pants region”, which includes the hind legs and feet, lower back and tail base, and belly. However, other pets will be itchy all over, around the ears, neck, face, etc. Diagnosis of flea allergy includes finding fleas or flea dirt on the pet, as well as response to treatment. Treatment starts with getting your pet on reliable monthly flea prevention from your veterinarian, and products should be used year-round. We never know if we will get a frost cold enough to kill all fleas in the outdoors (especially with the crazy weather in Northeast Ohio!), and fleas can be very tricky and live hidden indoors as well. It is necessary to treat all animals that are in direct contact with your flea allergic pet, including cats or dogs who are indoor-only and do not travel outside. We can bring fleas into the environment on our clothes, and they can live and multiply on our pets and in the environment from that point on. Therefore, it is also KEY to completely eradicate fleas from the environment that the pet lives in at home. We have handouts available on treating your house and environment available in our office, and attached here.

Food Allergy (food hypersensitivity, cutaneous adverse food reaction):

Just as humans can be allergic to certain foods, our pets can also develop food allergies and sensitivities. Dogs and cats must have a prior exposure to the food in the past to become allergic to it, which may include diets the pet has been on for years. Often times animals are allergic to particular proteins in diets (beef, chicken, dairy products, wheat, corn, etc.), but they really can be allergic to any type of food. Food allergic dogs can present with itchiness all over the body, or in very particular areas (feet only, ear infections only, etc.). Other signs for food allergic pets may include gastrointestinal signs such as vomiting and diarrhea (which may be off and on). Most food allergic dogs and cats will be affected year-round, especially if the food allergy is to a food they receive on a regular basis. Diagnosis is made by embarking on a food trial, in which the animal is fed a new diet with no additional foods. The pet is placed on a prescription hypoallergenic diet, which are either a novel protein or hydrolyzed protein diet. Novel protein diets are ones that include simple ingredients (one protein and one carbohydrate source) that the pet has never been exposed to in the past (such as rabbit and potato, venison and green pea, even kangaroo and oats!). Also available are diets including hydrolyzed proteins, in which the proteins are broken down into tiny pieces too small for the immune system to recognize as an allergen. It is VERY important that the pet not be fed any treats, table scraps, flavored medications or other foods during the food trial. The diet needs to be fed for at least 8-12 weeks to see an improvement; some pets take longer than others to respond. If an improvement is seen, the only way to truly demonstrate that a pet is food allergic at this point is to “re-challenge” the pet’s system with the old diet to prove that the improvement was based on diet change and not due to other factors (including medications or seasonal change). Treatment includes long-term maintenance on the diet that works for your pet.

Atopy (environmental allergy, atopic dermatitis):

Atopy is an allergic disease resulting from exposure to certain environmental allergens. Atopy can be seasonal (pollens, grasses, trees, etc.) or non-seasonal (dust mites, molds, dander, etc.). Pets can be itchy anywhere on the body or in specific areas (feet, ears, etc.), similar to the other types of allergies. Therefore, it is crucial to rule out food and flea allergies as well as other causes of itchy skin (i.e. skin parasites and infections) before diagnosing your pet as having atopic dermatitis. Further diagnostics include history (seasonality and symptoms of the pet), response to certain medications, skin allergy testing and blood testing. Once atopy has been diagnosed, treatments are many and can include antihistamines, fish oil, vitamins, steroids used on limited basis, topical shampoos and lotions, allergen hyposensitization injections, as well as cyclosporine and other new developing atopic medications.

Determining the trigger for allergies can be challenging, but starting with a visit to your vet with a good history of your pet’s food, treats, environment, toys, and current medications is a great first step. Once in the office, we will ask many questions about your pet’s itchiness and thoroughly examine your pet; from there we will determine which tests to begin in order to get the ball rolling on diagnosis of your pet’s allergies.

Allergic disease can be frustrating for everyone involved- the pet, the owner, and the veterinarian. Each allergic animal responds differently to treatment options, and part of the frustration is finding what works for your individual pet. What works for one pet often doesn’t work exactly the same for another- just part of the “fun” of figuring out the puzzle! Even though there is no true cure for allergic disease in pets (and they will have this disease for the rest of their life), we are often able to manage and control allergies in pets. Often different medications and combinations of treatments need to be tried before finding the right fit for comfort in each pet, but together we can work to help our pets lead comfortable lives.

Jessica Murphy, DVM

Stow Kent Animal Hospital



Check out our video made by Dr. Albers as she discusses allergies


Additional Resources


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