Allergies in Cats

Written by Small Door's medical experts

Does your cat seem itchy? Do they sneeze often? Do you notice an increase in itching and sneezing during specific seasons of the year? If so, your cat may be experiencing allergies. Read on to learn more about allergies in cats, and how they are diagnosed and treated.

In this article:

What are allergies in cats?

Allergies, reactions in the body or skin to something that is usually harmless, occur in some cats after exposure to an allergen. Allergens may activate your cat’s immune system to produce a blood protein called an antibody (also known as an immunoglobulin). Repeated exposure to an allergen may lead to an overproduction of your cat’s antibodies, which in turn tells your cat’s body to have an inflammatory response through the release of histamines. 

Allergens come in many forms. For example, your cat could be exposed through inhalation or absorption through the respiratory system, skin, or gastrointestinal system. 

Types of allergies in cats

Cats and kittens may experience different types of allergies. These include:

  • Airborne (environmental) allergies 

  • Food allergies

  • Flea allergies (also referred to as flea allergy dermatitis)

Sometimes, cats may also develop a condition that is secondary to an allergy or hypersensitivity called eosinophilic granuloma complex, which results in a few different types of skin lesions.

Signs & symptoms of allergies in cats

Like humans, cats may exhibit different signs and symptoms of allergies, which may include:

  • Itching (your cat may exhibit scratching, chewing, or excessive grooming, which may lead to pain and inflammation)

  • Skin rashes, lesions, scabs

  • Hair loss (also called alopecia)

  • Gastrointestinal upset (such as diarrhea, vomiting)

  • Sneezing

  • Coughing or wheezing, difficulty breathing, feline asthma

  • Runny eyes 

  • Runny nose

  • Ear infections (often indicated by head shaking, scratching the ears, smelly ears)

Causes of allergies in cats

Cats may experience seasonal allergies just like humans. Known as atopy or atopic dermatitis, this type of allergy is caused by airborne allergens, such as pollens or dust mites. Usually, atopy manifests as very itchy skin, fur loss, excessive licking of the skin, or ear infections. Sometimes, if a cat is overly itchy and excessively scratching, the scratching itself may lead to the development of a secondary skin infection, so it’s a good idea to keep a close eye on your cat’s skin. 

Food allergies are caused by a reaction or hypersensitivity to a specific ingredient (or multiple ingredients) in your cat’s diet. Often, cats may be allergic to a specific type of protein (such as chicken), a carbohydrate source (such as peas, rice, or potatoes), fillers added to bind the food (wheat is a commonly used filler), preservatives, or dyes. Symptoms of food allergies may show up through skin symptoms or gastrointestinal symptoms, such as vomiting and diarrhea. 

Fleas are the most common cause of skin allergies in cats. It is important to note that even if you don’t see any visible evidence of fleas on your cat, it is still possible that they are experiencing flea allergy dermatitis, as the allergic response is actually triggered by the saliva of the flea. This means that even just a few bites from a flea may cause an allergy flare. Also, your cat may be removing all evidence of fleas through excessive grooming due to allergic itch and discomfort. 

Diagnosing allergies in cats

Your veterinarian may be concerned about atopy, or atopic dermatitis, based on a thorough history, physical exam, and after ruling out other causes of itchy skin. They may recommend diagnostics such as an allergy blood test or they may recommend intradermal skin testing through a local Veterinary Dermatologist. 

With intradermal skin testing, a small area of your cat’s skin is shaved, and they are then given multiple injections of very small amounts of different types of allergens (such as dust mites, pollen, mold, etc.) in a grid formation on the skin. If any of the injection sites show an inflammatory response by becoming red, irritated, and itchy, that indicates that your cat has an allergy to that specific allergen. Your cat will typically be sedated to allow for this testing.

Blood testing involves collecting a sample of blood and submitting it to a lab for testing. At the lab, they will check the sample for antibodies that would develop in response to several different kinds of allergens. 

Diagnosing food allergies in cats is a diagnosis by exclusion, as there is no accurate blood test currently available to test for food allergies in cats. Your veterinarian may guide you through this process. The primary way this is done is through a food trial, which eliminates potential allergens by strictly feeding your cat a hypoallergenic diet for several weeks to months. In general, if your cat’s symptoms disappear after starting the new hypoallergenic diet, it helps to confirm that they in fact do have a food allergy. Additionally, if your cat’s symptoms are constant year-round and do not appear to be seasonal in nature, it may be an indication that a food allergy is at play rather than an environmental/seasonal allergy. Some environmental allergens can be present all year, such as dust mites, which can cause signs all year and would not improve with a diet change. There can also be a combination of food and environmental allergies, further complicating diagnosis.

Your veterinarian will perform a physical exam of your cat to rule out fleas as an underlying cause. Since fleas may not always be visible in the case of flea allergy dermatitis, this allergy is diagnosed through prophylactic treatment using topical or oral flea medications. If your cat’s symptoms dissipate after treatment, it confirms the diagnosis of flea allergy dermatitis. 

Treatment of allergies in cats

While treatment of allergies in cats is dependent on the underlying cause, typically your veterinarian will first treat the signs and symptoms of the allergy or any secondary bacterial or fungal infections. However, while this will help relieve acute symptoms, it will not resolve them long term. Your veterinarian can help identify the underlying cause and recommend a treatment plan. 

Common treatments for signs and symptoms, as well as underlying causes of allergies, may include: 

  • Antihistamines

  • Immunosuppressants (such as Atopica, a brand of cyclosporine)

  • Corticosteroids (such as prednisone, prednisolone, methylprednisolone)

  • Antibiotics

  • Antifungals (such as ketoconazole, fluconazole)

  • Hypoallergenic diets

  • Flea medications 

  • Allergen-specific immunotherapy (ASIT; also referred to as allergy injections)

  • Sublingual immunotherapy (SLIT; this is when immunotherapy drops are placed under the tongue and absorbed through the mucus membranes or gums within the mouth)

Is there a cure for allergies in cats? 

Depending on the underlying cause of an allergy, cats may sometimes be cured of their allergy. For instance, if they are experiencing flea allergy dermatitis, once the flea infestation has been treated, the signs and symptoms associated with the dermatitis should also resolve. The flea allergy will still remain, but the cat should not have any clinical signs (dermatitis) or discomfort if kept on monthly parasite prevention.

Immunotherapy may be successful in treating your cat’s environmental allergies. Patience is key, as symptoms may initially become worse with therapy as your cat becomes desensitized to certain allergens with injections or drops. According to the Merck Veterinary Manual, it may take about a year to see the results of immunotherapy, which may result in less severe allergy symptoms in the next season for many cats. 

While atopy sometimes cannot be cured and your cat may endure an “itchy season” each year, their allergies may be medically managed to keep them as comfortable as possible and reduce the overall severity of their symptoms. 

If your cat is diagnosed with a food allergy, they will need to continue lifelong treatment with their hypoallergenic diet. This means strict adherence to the diet (no treats or other foods that are not also hypoallergenic) in order to control their symptoms. 

Are allergies in cats contagious for humans or other pets? 

Allergies are not contagious for humans or other pets. However, humans or other pets may exhibit similar symptoms if they happen to also have an allergy or allergic response to the same type of allergen.

Recovery & management of allergies in cats

Usually, once the underlying component of a cat’s allergies are diagnosed and treated, they will make a full recovery and only experience flare-ups of their allergies depending on the season or exposure to a specific allergen. The use of immunotherapy has also been found to greatly reduce the symptoms of allergies in cats.

Signs and symptoms of allergies in cats may be medically managed through the long-term use of certain medications (such as immunosuppressants or antihistamines) or hypoallergenic diets. However, some medications (such as corticosteroids) should not be used for an extended period of time in cats, as they may cause metabolic side effects in cats. It is also important to keep your cat up to date with their flea prevention to avoid the development of flea allergy dermatitis. 

How to prevent allergies in cats

While allergies are not entirely preventable, you may take steps to reduce exposure to allergens. This may include adherence to monthly flea preventatives and avoiding the use of potential irritants or allergens in the home (such as strongly perfumed candles or cleaning supplies). 

Allergy injections or immunotherapy treatments may not prevent all future allergic flare-ups, but they may help to minimize the severity of symptoms. 

Is there a vaccine for allergies in cats?

There is no vaccine to prevent allergies in cats. However, there are immunotherapy treatments that, like a typical vaccine, may be administered in the form of subcutaneous injections.

Summary of allergies in cats 

While an allergy may be a complex condition to diagnose and treat in cats, it is a completely treatable and manageable condition, and in some cases may resolve completely. With the proper treatment and reducing exposure to your cat’s allergens, your cat may still have a great quality of life with fewer allergy flare-ups. 

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