I Think My Pet is Allergic to Something, Now What?

Many people experience allergy symptoms – red, itchy, watery eyes, sneezing, and a runny nose. You may even suffer with these symptoms yourself. Pets can develop allergies, too, though their symptoms may be different than what we expect or experience.

Allergies are an overreaction of the immune system to a foreign substance. Normally, the immune system is constantly on guard protecting the body from foreign invaders. When a foreign substance is found, the immune system creates antibodies to eliminate it from the bloodstream. When the foreign substance is something that causes infection, like bacteria, the immune system’s reaction protects the body from harm.

Unfortunately, sometimes the immune system identifies innocent, or benign, foreign substances as harmful, even though they are not. Some examples would be pollen, food proteins, or dead skin cells. The immune system’s overreaction to these substances can cause harm to the body by increasing inflammation to the skin, respiratory, or digestive systems. This overreaction usually occurs after being exposed to a substance over months or years.


There are several types of allergies that pets can experience. The first is a flea allergy. When a flea bites to get a blood meal, it injects some of its saliva into the victim. Some pets develop an allergic reaction to the proteins in the flea’s saliva. A pet doesn’t need to have a lot of fleas to develop this problem. Once the allergy exists, a reaction can occur to a single flea bite.

The pet frequently will experience itching and hair loss midway down the back, around the base of the tail, and down the rear legs. This allergy can occur any time during the year, but may be more of a problem during the warmer months when fleas are more active. To reduce allergy outbreaks, it is important to avoid fleas by giving the pet flea preventative and ensuring their environment and contacts are free of fleas.

Another type of allergy that pets may experience is an inhalant allergy. This is an allergy due to substances breathed in from the environment. Depending upon the allergen, it may be seasonal, like with pollen and ragweed, or it may be present all year long, as with dust mites and mold spores.

Pets with this type of allergy will feel itchy all over their body. They will try to lick, bite, chew, rub, or scratch themselves to get rid of the itch without success. Areas around the ears, eyes, armpits, groin, and feet are most often affected. Hair loss is usually patchy. The skin may be red and thickened in affected areas. There may also be hot spots of moist, reddened, oozing areas on the skin. Ear or skin infections may occur due to bacteria or yeast growing in the allergy affected areas. Occasionally, pets may develop breathing issues as well.

The third type of allergy that pets may experience is a contact allergy. This can occur after repeated exposure to a material or chemical in their environment. Some possible allergens are flea collars, pesticides, insecticides, carpets, wool, synthetic fibers, metals, leather, plastics, cleaning solutions, and topical medications.

Pets develop itching and irritation in skin areas that come in contact with the allergen. This often involves areas not well protected by the pet’s hair such as the chin, chest, abdomen, groin, and feet. The affected skin areas become red and thickened. There may be hair loss, oozing, and crusting. Secondary bacterial infections may occur due to pets licking, chewing, or scratching the affected areas. Finding and removing the contact allergen from the pet’s environment is important to avoid repeat episodes.

The fourth type of allergy that pets may experience is a food allergy. This type of allergy is less common in pets, than environmental or flea allergies.  With a food allergy, the immune system overreacts to a substance that is eaten. It sees it as an invader, rather than as normal food. The allergen is usually a protein, but sometimes it can be a carbohydrate. Some typical foods that can cause allergies in pets are chicken, beef, dairy, egg, soy, lamb, rabbit, wheat, and fish. A food allergy can occur even if the pet has been on the diet for a long period of time.

When a pet has a food allergy, they may have many of the same skin issues discussed earlier – itchy skin, skin infections, and ear infections. This makes it difficult at times to determine the exact cause because flea and environmental allergies also have skin manifestations. Pets with food allergies may also have digestive problems like vomiting or diarrhea. Just keep in mind, that digestive problems have multiple causes as well, such as parasites, infections, and pancreatitis, so be sure to consult your veterinarian.

The best way to resolve a food allergy is to avoid the food that triggers the problem. This is easier said than done, because food diets contain so many different ingredients. To determine the cause of the food allergy, the pet must be placed on a food elimination diet for at least 8 to 12 weeks. During this time, the pet is given a special diet, different than the one they were eating. This may be a hypoallergenic diet. It could also be a hydrolyzed diet, in which the proteins are broken down into small pieces, so they don’t cause an immune reaction. It is important that the pet does not eat any other food or treats during this time. If the pet improves on the diet, then your veterinarian can conduct challenge testing to determine which food might be causing the allergy.

The final type of allergy is bacterial hypersensitivity. This is an overreaction of the immune system to the Staphylococcus bacteria that are normally found on the skin. This frequently occurs in pets that already have another type of allergy or untreated hypothyroidism. Skin that is dry and irritated can become infected, especially when pets continue to lick, chew, and scratch the irritated skin or an open wound. Most bacterial infections can be easily treated with antibiotics. However, pets with this allergy may require a longer period of antibiotic treatment. Allergic flare ups can occur if treatment is ended too quickly.


When your pet is having problems with allergies, there are treatments that can ease their discomfort. First of all, there are medicated shampoos that can soothe their itchy, irritated, and inflamed skin. The shampoos also contain antibacterial or antifungal agents to reduce infection, as well as ingredients to keep the skin and hair coat from drying out. Bathing your pet every week helps to decrease the allergens that are attached to their skin and hair coat.

Antihistamines work by disrupting the release of histamine in the allergic reaction. This decreases the itching and inflammation for some pets. These medications have few side effects. Sometimes different antihistamines need to be tried before the right one is found that works best for your pet. They are usually inexpensive and frequently effective.

Corticosteroids can reduce the itching and inflammation caused by allergies over a period of several days. However, steroids have their own risks. Short term side effects include changes in behavior as well as increased thirst, urination, appetite, and weight gain. Prolonged use of steroids can cause liver damage, diabetes, and an increased risk of infections. If steroids are used, the benefits should be carefully weighed against the risks.

Oral cyclosporine (Atopica) is a medication that reduces the allergic reaction by suppressing the body’s immune response. When taking this medication, the pet shows improvement over a period of weeks. Possible side effects include loss of appetite, vomiting, or diarrhea. As with any medication that suppresses the immune system, there is the possibility of an increased risk of infection. Cyclosporine has shown less long term side effects than corticosteroids. However, the medication can be expensive, especially when treating a larger pet.

For certain allergies, the best treatment is avoidance or desensitization. Allergy testing can be helpful in identifying the substances that cause allergic reactions in your pet. One method of allergy testing can be performed using blood tests looking for antigen induced antibodies in the blood. The most ideal method is allergy skin testing. In this method, a portion of the pet’s hair is shaved, then different antigens are injected into the skin in a known pattern. If the pet is allergic to an antigen, there will be a raised, red area that appears in a few hours. Once the results of the testing are known, then action can be taken.

If the antigen is something that can be avoided or removed from the pet’s environment, then the allergy can be controlled. However, some antigens, like pollen, can’t be avoided. In those cases, an allergy shot can be created that contains the antigens, first in very small doses, then increasing the dose slowly over time. Over a period of weeks to months, the injections modify the pet’s immune system, so that it doesn’t overreact to the allergen.

Monoclonal antibody injections (Cytopoint, CADI) are another possible treatment for allergies, but only in dogs. These antibodies target a unique chemical in the immune system, called interleukin-31 (IL-31). This is a chemical that promotes itching in the immune response. By blocking this chemical, itching can be stopped in a couple of days. The benefits of the injection usually last a month, but it may be longer in some dogs. The main side effect is discomfort at the injection site. Since it only targets one chemical, it has the added benefit of not suppressing the rest of the immune system. The injections are expensive, but a monthly injection may be preferred over other medications that require daily dosing or have more side effects.

It can take time to get to the root cause of allergies in your pet. Once the problems are identified, then appropriate steps can be taken to treat them. Though allergies can’t be completely cured, they can be managed and minimized to give your pet an improved quality of life.


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