Allergies in Cats

Lauren Jones, VMD
By Lauren Jones, VMD on Aug. 29, 2022
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In This Article


What are Allergies in Cats?

An allergy is an immune response sensitivity to certain substances that cause allergic reactions. These are classified as antigens or allergens. Typically, allergens are inherently harmless (like pollen, foods, or dust), but in certain individuals, the body overreacts and stimulates an inflammatory response that causes allergy symptoms.

Humans with allergies typically have symptoms like itchy, watery eyes, sneezing, and a runny nose. Our feline companions may also have these issues, but more commonly display allergies in a combination of the following body systems:

  • Skin: Itchiness can cause cats to lick, chew, or rub their skin and fur, leading to infections and hair loss. The skin is the most affected organ system.

  • Gastrointestinal: Symptoms usually show as vomiting or diarrhea.

  • Respiratory: This includes the lower and upper airways, often with nasal discharge.

  • Ocular: Allergens often cause conjunctivitis.

Allergies are extremely common in cats and it’s typically a life-long condition that can impact the cat and pet parent’s quality of life. While some breeds may be more prone to allergies, they can occur in all cats. Early intervention is critical to long-term success. As soon as you notice your cat may be suffering from allergies, call your veterinarian for an exam.

Types of Allergies in Cats

The term “allergy” is a general label. Veterinarians recognize these six major types of allergies in cats:

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Symptoms of Allergies in Cats

All types of allergies can cause similar, overlapping clinical signs in cats. These symptoms vary in intensity and may develop over years.

Food Allergy

Food allergies can look very similar to environmental allergies. Not all cats with a food allergy will have gastrointestinal signs like vomiting, diarrhea, flatulence, and hypersalivation. Many will have skin symptoms, including itchiness, especially around the face, head, and neck. Food allergies are typically non-seasonal, meaning they occur all year round.

Atopic Dermatitis

Atopy, or environmental allergies, can mimic food allergies. Itchiness is the most reported clinical sign, in addition to ear infections, hair loss, skin plaques, and pustules. Often, cats have relapsing secondary bacterial and yeast infections. Atopy can also cause asthma-like respiratory issues, and conjunctivitis.

Flea Allergy Dermatitis

Flea allergies only affect the skin. Historically, cats with flea allergies either have poor or no flea control.   The head and neck are most often affected, as well as the inner thighs and abdomen. Often, cats have intense itching resulting in self-induced trauma from itching, chewing, and rubbing to relieve the itch.

Allergic Contact Dermatitis

Allergic contact dermatitis occurs as lesions on the skin after exposure to a certain trigger such as pollen, yeast, or mites. The location is determined by direct contact. Most cats with contact dermatitis show redness, swelling, pustules, and crusts at the site of exposure. Itching at these locations may be moderate or severe.

Cutaneous Drug Eruptions

Cutaneous drug eruptions are allergic reactions to any type of drug. They vary in clinical signs, location, and severity. Cats most often experience itchiness, rashes, redness, swelling, inflammation, hives, and in severe cases, cellular death and sloughing of the skin in sheets. This type of allergy is uncommon in cats.

Allergic Bronchitis

Allergic bronchitis is also known as asthma. Cats will typically wheeze, cough, and have labored breathing.

Causes of Allergies in Cats

Food Allergy

The cause of food allergies in cats is poorly understood. Any protein, carbohydrate, preservative, additive, or dye can be potentially allergenic. Typically, a cat’s immune system is overstimulated by a protein. The most frequently reported allergies are beef, fish, and chicken. While cats can have allergies to grains, corn, or gluten, it is far less common than the main protein sources. Some studies indicate Siamese cats and cats under six months may have higher rates of developing food allergies.

Atopic Dermatitis

Atopy, or environmental allergies, is characterized by inflamed, itchy skin disease. Genetic causes are not well documented in cats, but atopy occurs more often in Abyssinian, Devon Rex, and domestic short-haired cats less than 3 years old. The most common causes of atopy are:

  • Pollen

  • Mold spores

  • Yeast

  • Dust and storage mites

  • Animal or human dander

Flea Allergic Dermatitis

Flea allergic dermatitis occurs as a hypersensitive reaction to the flea’s saliva.

Allergic Contact Dermatitis

Allergic contact dermatitis is rare in cats and involves a delayed hypersensitive reaction at the site of contact with:

  • Plants (pollen, grasses, trees)

  • Medications (topical drugs, ear medications, soaps, shampoos, insecticides)

  • Home furnishings (fibers, dyes, polishes, cleansers)

  • Other (rice flour, chlorinated water)

Cutaneous Drug Eruptions

Any drug can cause a cutaneous drug reaction. It can happen after one dose or multiple doses. More common drugs that cause a drug eruption include antibiotics, anticonvulsants, antihypertensives, NSAIDs, and antiarrhythmic drugs.

Allergic Bronchitis

Asthma occurs when a cat’s immune system overreacts to allergen in the air causing airway inflammation and constriction of the airway. Cigarette smoke, poor environmental hygiene, dusty cat litter, hair spray, molds, pollen, powders, household chemicals, and air fresheners are all potential inciting allergens.

How Veterinarians Test for Allergies in Cats

Food Allergy

In cats with a suspected food allergy, a dietary elimination trial is the main diagnostic method. While you can purchase saliva test kits online or submit blood work to test for food allergies, there is currently no reliable data to suggest these tests are accurate.

A diet trial is typically done in one of two ways:

Novel protein diets remove the inciting allergen (beef, chicken, or fish) and instead offer the cat a new, or novel, protein that their immune system has never seen and, therefore, likely will not have a reaction to. Common novel proteins include whitefish, salmon, turkey, kangaroo, rabbit, duck, and venison.

Hydrolyzed protein diets contain ingredients that have been broken down into the smallest possible molecular weight so that they do not elicit an immune response.

Diet trials may take two to three months before there is a clinical improvement. They can be frustrating and difficult to interpret because of concurrent other types of allergies and compliance. During the diet trial, the cat cannot have any other food, treats or human food without affecting the outcome.

Atopic Dermatitis

Veterinarians use two main tests to diagnose specific environmental allergens:

A serology allergy test measures allergen-specific reactions in the blood. This is a simple test that most general practitioners can readily perform.

Intradermal testing is the gold-standard diagnostic test performed by veterinary dermatologists. Test allergens are injected into the skin and will form a wheal, or swelling, if the cat is sensitive to that antigen. This typically requires sedation.

Flea Allergy

Finding fleas and flea dirt can help diagnose a flea allergy but is not required. A flea comb is useful to identify fleas.

Blood tests (the same used for atopic dermatitis) can be used to help diagnose an allergy to fleas. Many veterinarians will treat for a flea allergy based on clinical exam and history alone. Response to treatment with appropriate flea prevention often provides the diagnosis on its own.

Allergic Contact Dermatitis

Finding the cause of allergic contact dermatitis is true detective work, taking significant time and investment from the pet parents. To test for allergic contact dermatitis, veterinarians perform a patch test. Materials from the house or outdoor area are applied to areas on the body and checked daily for 7 to 14 days. Biopsies are also useful in cases of suspected contact dermatitis.

Cutaneous Drug Eruption

Drug reactions are typically diagnosed with a history of drug administration right before the cat became sick and recovery occurring when the drug was discontinued. Any drug can cause a skin reaction, but some have a higher prevalence and may raise a veterinarian to be suspicious.

Allergic Bronchitis

Asthma is most often diagnosed on radiographs, or X-rays. Veterinarians will likely also perform blood work to determine overall health and may perform cultures to rule out other diagnoses.

Treatment for Allergies in Cats

Food Allergy

Most food allergies are treated by eliminating the offending food from your cat’s diet.

During flare-ups, treatment is supportive and based on the clinical signs present. Steroids, antibiotics, anti-diarrheal, antihistamines, and anti-nausea medication may all be used for acute cases.

Atopic Dermatitis

Immunotherapy, or allergy vaccine, is the preferred method to treat atopy. These vaccines can be given as an injectable, or under the tongue. The formulations are specifically made based on the test results and individual allergens but can take from three months to one year for full effect.

Immunosuppressive drugs, like cyclosporine may bring allergy symptoms under control faster than immunotherapy, usually within a month. However, this medication requires more blood work monitoring due to its ability to suppress the immune system.

During severe episodes, cats may require supportive care based on their clinical signs. Medications may include:

  • Steroids

  • Antibiotics and antifungals for secondary infections

  • Pain medications

  • Topical therapy

  • Antihistamines

Flea Allergy

Cats with a suspected or confirmed flea allergy should receive flea control treatment. It is important to use only those products made specifically for cats. Most products come in a topical liquid or collar. Based on the flea’s lifecycle, these cats must be treated for at least 3 consecutive months in addition to environmental decontamination.

Supportive therapy may be required in the early phases. Cats frequently have secondary infections and may need antibiotics, steroids, anti-inflammatories, or topical therapy.

Allergic Contact Dermatitis

Once identified, the offending substance should be removed as a primary method of treatment. Hypoallergenic shampoos and wipes may help remove the offending allergen, but (as pet parents know) not all cats are happy with this treatment.

Other treatments include topical therapy, steroids, immunosuppressive and immunomodulating drugs.

Cutaneous Drug Eruptions

Most cutaneous drug eruptions are treated by stopping the offending drug. Some cases may require supportive care, hospitalization, and pain management. Severe reactions may require immunosuppressive therapy.

Allergic Bronchitis

Treatment for asthma is based on severity of clinical signs. For some cats, simply removing the allergen will improve symptoms. Unfortunately, determining the cause is often difficult, which means daily medication with steroids, bronchodilators, and immunotherapy may be required. Cats in respiratory distress require hospitalization and oxygen supplementation.

Difficulty breathing is a medical emergency. If your cat is breathing with its mouth open or has labored breathing, seek veterinary care immediately.

Recovery and Management for Allergies in Cats

With time, the commitment of loving pet parents, and a close relationship with a veterinarian, allergies can be managed, and your cat can enjoy a good quality of life. Allergies cannot typically be cured, but with monitoring and early intervention if flare-ups do occur, cats can quickly return to normal.

Risk factors, especially with cats with atopy, include environments with long allergy seasons and high pollen levels. Cats with multiple types of allergies are more difficult to diagnose, treat, and manage.

In addition, some allergies like flea allergies and contact dermatitis, become more severe and chronic as cats age. Work with your vet to determine the best treatments to manage your cat’s allergies, given the specific diagnosis and its personality.

Allergies in Cats FAQs

How can you tell if your cat has allergies?

Cats with allergies typically have skin issues and are itchy. This doesn’t mean they have allergies, but it is a possibility. Only testing with your veterinarian can determine if your cat has allergies.

What can I give my cat for allergies?

Always talk to your veterinarian before administering any medications or supplements. Based on your cat’s specific allergy, it may be treated with a combination of food and medications.

What are the most common allergies in cats?

Food allergy and environmental allergies are the most common.


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Lauren Jones, VMD


Lauren Jones, VMD


Dr. Lauren Jones graduated from the University of Pennsylvania School of Veterinary Medicine in 2010, after receiving her bachelor's degree...

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