How Can You Tell if Your Cat Has Allergies?

Most signs of allergies in cats affect the skin. Because they can resemble signs of nonallergic skin disease, accurate identification of allergic symptoms is important to restoring your cat’s comfort and well-being. Determining the type of cat allergy is also essential, because it will guide the treatment approach you and your veterinarian decide to take.

Diagnosing Allergies in Cats

There is no single test that identifies every type of allergy in cats or even whether your cat’s symptoms are caused by an allergy or another condition. Your veterinarian will rely on a combination of physical exam findings and other tools to rule out other possible causes for your cat’s symptoms. Some of these tools take time, so patience and dedication to the process may be necessary.

What Your Veterinarian Will Want to Know

Before your cat’s appointment, it helps to observe and jot down a few key details. Your veterinarian will ask questions to better understand your cat’s lifestyle, symptoms and environment. Being prepared can make the visit more productive and lead to a faster diagnosis.

Here are some things to pay attention to:

• When did the symptoms start? Try to note the first time you noticed any itching, hair loss or skin changes.
• Do the symptoms come and go? Let your veterinarian know if the signs seem to be seasonal or if they are present year-round.
• Where are the symptoms showing up? Be specific about the areas affected – such as the head, neck, belly or tail base.
• Has anything changed recently? This includes food, treats, litter, cleaning products or anything new in your cat’s environment.
• Does your cat go outside or live with other pets? This can help your veterinarian assess exposure risks to fleas, mites or allergens.
• Which flea protection are you using? Note the product name and how often you apply it.
• Has your cat had similar issues before? If so, describe how they were treated and whether those treatments helped.

Bringing this information to your appointment gives your veterinarian a clearer picture and helps guide the next steps in diagnosing and managing your cat’s allergies.

What the Veterinarian Looks For

Your veterinarian will check areas commonly affected by allergies, including the head, neck, belly, back, legs, paws, ears and around the tail. They will also examine the mouth for ulcers or lesions. Flea combing helps identify fleas or flea dirt, and an ear exam checks for inflammation that can occur with both environmental and food allergies in cats.

Other Tools

To rule out other skin problems, your veterinarian may recommend:

• Skin and ear cytology to check for bacteria or yeast
• Skin scrapings to look for mites
• Fungal culture or polymerase chain reaction (PCR) to check for ringworm
• Trial treatment with flea and mite control
• Skin biopsy if symptoms are unusual or not improving

Diagnosing Food Allergies in Cats

Protein sources such as beef, chicken and fish are the most common food allergens for cats. The only reliable way to diagnose a food allergy in cats and to identify which allergen is responsible is with an elimination diet trial (often called a “food trial”). This involves feeding a hydrolyzed diet, like Purina® Pro Plan® Veterinary Diets HA Hydrolyzed Feline Formula, or a novel protein diet – that is, one with a protein source the cat hasn’t eaten before – for 8–12 weeks. If symptoms improve, the original food is reintroduced to confirm the allergy.

Your cat should not be given any other food, including treats, during this trial without your veterinarian’s approval. If a therapeutic diet is not financially possible, a novel protein diet may be used with the understanding that results are often not as accurate.

(You may have heard of hydrolyzed diets being referred to as “hypoallergenic cat food.” Hydrolyzed means that the protein in the food has been broken down into a small enough size that the cat’s body doesn’t recognize it as an allergen. Thus, these diets can be considered hypoallergenic, or having little chance of causing an allergic reaction.)

Allergy Testing in Cats

Allergy testing may be recommended to help guide treatment, particularly when considering immunotherapy. However, it is important to understand that allergy tests for cats, whether blood (serum) or intradermal, do not confirm whether a cat actually has allergies. Their primary purpose is not to diagnose allergy but to identify relevant environmental allergens and formulate a customized immunotherapy plan. Among the available methods, intradermal testing is considered the method of choice for identifying specific allergens but often requires referral to a veterinary dermatologist.  

When a Referral May Help

If your cat’s condition is severe, complex or not improving, your veterinarian may recommend seeing a veterinary dermatologist. These specialists can offer advanced testing and treatment options for allergies in cats.