Allergies in Cats

Key Takeaways

Allergies are common in cats, similar to other species. Harmless proteins in the environment (allergens) stimulate the immune system, which overreacts and produces a strong inflammatory response.

• The most common allergens in cats are flea saliva, grass, pollen, and animal proteins in the diet

• Cats with allergies are usually extremely itchy, and often damage their skin in the process of scratching

• Watery eyes, a runny nose, or vomiting and diarrhea are other, less common symptoms

• To arrive at a diagnosis of allergies, several tests are run to rule out other causes of itchiness, such as parasitic or bacterial infections

• Specific allergens are identified by exposure and elimination testing

• Treatment includes eliminating allergens, immunotherapy, and allergy medications

A Closer Look: What Are Allergies in Cats?

Allergies are a common condition in cats, and cause sufficient itch that interferes with quality of life and puts them at risk of secondary skin infections. Even though being itchy is not life-threatening, allergic cats require prompt veterinary care to diagnose any underlying conditions and start appropriate treatment for timely relief. Identifying the particular allergen causing the reaction and the best management strategy takes a significant amount of trial and error. With appropriate management, many cats have their symptoms reduced, however complete resolution is not expected. A cat with allergies is expected to develop symptoms any time it is exposed to its allergens if it is not on medication.

Risk Factors

Besides itchiness, other symptoms of allergies include:

• Watery eyes • Runny nose • VomitingDiarrhea

Cats that are severely itchy often cause damage to their skin and ears. In some cases, an infection develops. Symptoms of skin damage and infection include:

• Redness, swelling, or crusting of the skin • Hair loss • Scratches or scrapes • Oozing or weeping sores

• Foul odor

An underlying allergy condition is suggested any time a cat has recurrent ear or skin infections.

Possible Causes

Allergies occur when the immune system overreacts to foreign proteins in the environment. The risk factors for developing allergies are unclear, particularly in cats where breed predispositions are poorly defined, but a genetic link is suggested.

There are several categories of allergies distinguished by the source of the allergen and route of exposure.  These categories are:

Contact allergies, including flea allergy dermatitisFood allergiesSeasonal allergies • Atopy (inhaled allergies)

 The most common allergens in cats are:

• Grass • Dust mites • Pollen • Flea saliva • Animal proteins in food

Main Symptoms

The most common symptom of allergies is itching (pruritus). The need to itch is often so severe that it interferes with the cat’s daily life. Signs of itchiness include:

• Excessive scratching • Chewing or licking an area • Rubbing on surfaces or rolling on the ground

Testing and Diagnosis

There are many potential causes of itching in cats, which makes diagnosing allergies difficult. Many diagnostic tests are needed to rule out other causes of itch before a diagnosis of allergies is made. These tests include:

• Physical examination • Testing for bacterial, fungal, or parasitic infections • Skin biopsies • Blood work 

Some types of allergies follow trends regarding when symptoms begin or worsen. These trends often help categorize what type of allergy is occurring. Based on the type of allergy, a list of possible allergens is made. From there, specific testing of each allergen helps identify which allergen is causing the issue. These tests include:

• Food elimination trials • Withdrawal testing • Patch testing

Intradermal allergy testing is available, and can be helpful in narrowing down a list of potential allergens. This process is similar to allergy testing in humans, where a small amount of allergen is injected into the skin and the injection site is monitored for an inflammatory response.

Steps to Recovery

In all species, allergies are generally managed, not treated. Some cats benefit from anti-itch medications. These medications do not treat the cause of itchiness, but instead interrupt the “itch signal” so the cat feels less itchy. Options for relieving the symptoms of allergies include allergy medications (pills and injectable) and steroids. Antihistamines are often not effective for relief of allergy symptoms in cats. 

The only potential cure for allergies is immunotherapy. In this treatment, a small amount of allergen is injected into the cat’s skin at regular intervals over a long period of time. After many injections, the immune system’s reaction to the allergen reduces. Immunotherapy often takes several months to a year to show an effect, and must be maintained for life in most cases.

There is no cure for allergies, so they are considered to be a life-long condition. Many cats’ symptoms improve with appropriate management and medications, however complete resolution of symptoms is uncommon.

Prevention

Allergies are not contagious. Since the root cause of allergies is unknown, it is not possible to prevent them, but reducing or eliminating exposure to known allergens is expected to resolve symptoms.   Strategies to reduce exposure vary depending on the type of allergy. Examples include:

• Diet change • Routine cleaning of the environment • Washing bedding regularly • Routine parasite control

• Air filtration to remove airborne allergens

Are Allergies Common in Cats?

Allergies are common in cats. Flea allergy dermatitis is the most common type of allergy, and studies suggest this allergy is becoming more common.

Typical Treatment

• Environmental modification • Anti-itch medications • Allergen immunotherapy • Dietary restriction

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