13 min

Allergies In Cats: Signs, Diagnosis & Treatments

Does your cat have allergies? Let's look at the different types of allergies in cats and their symptoms, diagnoses, and treatments.

Aly Walansky

Updated May 22, 2023 • Published April 02, 2021

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Allergies In Cats: Signs, Diagnosis & Treatments

Just as with humans, allergies can commonly be seen in our cats as well. An allergy is basically a very strong reaction from the immune system to a trigger that would usually be considered a normal part of the environment. This is also the reason why different individuals can live together in the same household without all experiencing the same symptoms.

The symptoms will vary depending on the type of allergy and the organ system that is mainly affected. Allergies can broadly be placed into respiratory, skin, and gastrointestinal (gut) categories, depending on the symptoms your cat experiences. 

Respiratory allergies in cats

Respiratory allergies are seen when normal substances in the environment cause a reaction from the immune system in the respiratory (breathing) tract. 

Causes for respiratory allergies can range from pollen in the air to dust mites, molds, perfumes, and cleaning products, to name a few. If you notice sudden symptoms of a possible respiratory allergy in your cat, it might be worth trying to think if anything changed in their immediate environment recently.

Asthma in cats is also a form of respiratory allergy that can have very serious consequences. These cats can sometimes be seen breathing with open mouths and the movement of the abdominal muscles will be exaggerated during breathing. These cats need to be examined and treated by a veterinarian as soon as possible. 

Symptoms of respiratory allergies in cats include:

  • Sneezing

  • Watery eyes and/or a runny nose

  • Red eyes

  • Changes in breathing rate or increased effort to breathe

  • Coughing

Diagnosis of respiratory allergies

There is no one specific test to diagnose respiratory allergies. Your vet will look for other possible causes for the symptoms first by taking a thorough history, doing a clinical exam, and possibly some blood tests and x-rays of the chest. They might also want to try to get some samples from the airways to see if there could be other causes for the symptoms. 

Treatment for respiratory allergies

The treatment for respiratory allergies depends on the cause and severity, as well as the duration of the symptoms. Treatment is aimed at trying to reduce the offending substances in the environment and reducing the allergic response to these substances. Treatment options could include:

  • Reducing the use of sprays in the house, not allowing any smoking in the house, using air purifiers or humidifiers, and switching cat litter to a no-dust variety

  • Allergy shots (allergen-specific immunotherapy)

  • Injectable, oral, or inhaled corticosteroids

  • Cyclosporine

  • Airway dilators

Some treatments may also have side-effects and your vet will have to balance all these factors to find the best possible solution for your cat—every individual case is different and there is no "one best treatment" for respiratory allergies in cats.

Skin allergies in cats

Skin allergies are very commonly seen in cats. The most common skin allergies are caused by fleas, airborne substances, and food. 

One of the most common causes of skin issues in cats is a flea bite allergy. Cats with flea bite allergies have a hypersensitivity reaction to the saliva of fleas, which means only one or two flea bites can be enough to start the process of itching and scratching. In fact, cats with flea bite allergies are very often not the ones crawling with fleas, as they will very quickly start to over groom and thus make it difficult to find fleas on them. Flea dirt (small black specks) can sometimes be seen between the fur on the back and belly, but this is not always the case.

Another common type of skin allergy is allergies to airborne substances (atopy). These allergies are seen when substances like pollens, dust, and molds normally found in the environment come in contact with a cat’s skin. In a cat with these skin allergies, the skin barrier is defective or abnormal and the irritants can thus pass this initial defensive barrier and lead to a direct reaction from the immune system. This will in turn lead to inflammation of the skin which results in itching, reddening of the skin, and ultimately, scratching and hair loss. You will often find these cats to be at their worst when the humans around them are suffering from hayfever, as they are often caused by similar substances.

Food can sometimes be a cause for some severe skin reactions. Food allergies can be seen even when the same food has been fed for years, so it's not always associated with a new food being eaten. In some cases, the cat will also suffer from vomiting or diarrhea as a result of the allergy.

Symptoms of skin allergies in cats include:

  • Excessive scratching, rubbing, or biting at the skin and/or ears

  • Hair loss

  • Scabby skin

  • Red and raw areas with or without scabs

  • Small scabs spread over the cat’s body, but especially on the back, neck, and around the head

  • Discharge from the skin

Diagnosis of skin allergies

Diagnosis depends on the symptoms your cat has, but can include:

  • Skin scrapes, fine flea comb and hair plucks

  • Skin biopsies

  • Allergy testing (skin tests or blood tests)

  • Response to corticosteroid or other treatment

  • Response to a food trial if food is suspected to be the culprit

Treatment for skin allergies

Treatment depends on whether a cause can be found and will be tailored according to each individual cat’s needs and response to treatment.

  • Flea bite allergies will be treated by routine flea preventative treatment for the cat and all other in-contact pets. The environment also needs to be treated with environmental sprays and regular vacuuming to remove adult fleas, intermittent flea stages, as well as flea eggs in the environment. It's very important to empty vacuum bags into tightly sealed plastic bags directly after vacuuming and ensure these bags are disposed of as soon as possible. Wash the cat’s bedding on a hot cycle in the washing machine to try to get rid of as many of the fleas and flea eggs as possible.

  • Reduce potential environmental allergens by avoiding the use of sprays, strong chemicals, and diffusers in the home and avoiding smoking in the house.

  • Medications such as corticosteroids and cyclosporine can be used to reduce the allergic response in the skin. These treatments are used as symptomatic relief.

  • Allergy shots (allergen-specific immunotherapy) that are tailor-made for an individual according to the results obtained during an allergy test can be effective.

  • Topical treatments such as special shampoos, mousse, and wipes can help to reduce the allergens on the skin and soothe the skin itself.

  • Supplements can help support the skin’s natural defense barriers. These supplements often contain omega 3 and 6 fatty acids.

  • Food trials can help to determine the ingredients that might be causing inflammation in the skin so it can be avoided in future.

This list is by no means exhaustive, and every case is individually assessed and the best treatment regime chosen to fit with the symptoms, possible causes, and other pre-existing disease conditions in the particular patient. Treatment can also be changed as needed.

Gastrointestinal (gut) allergies in cats

Cats with gastrointestinal allergies will often have symptoms of vomiting and diarrhea. These symptoms can go on for a long time depending on how severe the allergic response is and whether they are still eating the food causing the reaction. These types of reactions can sometimes be seen when new food or treats are introduced, although some cats can also suddenly start reacting to food they have eaten for a while. One of the more commonly known gut allergies is inflammatory bowel disease (IBD).

Symptoms of gastrointestinal allergies in cats include:

  • Diarrhea that can sometimes be chronic or intermittent depending on the cause for the allergic reaction

  • Vomiting

  • Weight loss

  • Itching accompanied by excessive scratching, scabs, and hair loss

Diagnosis of gastrointestinal allergies

The diagnosis of gastrointestinal allergies in cats is made if all other causes for the symptoms have been ruled out. Other tests can include:

  • Intestinal biopsies

  • Response to medication like corticosteroids

  • Response to food trials

Treatment for gastrointestinal allergies

Treatment for food allergies in cats consists of finding the ingredients that cause the allergic response and avoiding those in the diet. To do this, a food trial is completed. Your vet will discuss the use of hypoallergenic diets that either contain a novel protein (this is a protein your cat has never been exposed to) and a simple carbohydrate, or a hydrolyzed protein (proteins that are broken into such small particles the body cannot recognize it as a potential irritating substance).

This diet has to be fed exclusively for a period of around 6-8 weeks (sometimes extending up to 12 weeks). It's very important for everyone in the household to stick to this diet very strictly. This means no treats or flavored supplements can be used during this trial period. If the symptoms improve on the special diet, the next step is to reintroduce the original diet. It might seem like a bad idea at the time, but in reality, this is the only way of knowing for sure whether the original diet was the cause for the symptoms. If the symptoms do come back on the original diet, a diagnosis of food allergy can be made and a long-term plan in terms of the best diet will be made from there.

It's very important to realize that in a lot of cases, allergies can not be cured, as the causative agent/agents cannot always be identified or removed from the environment. In most cases, allergies will need to be managed life-long. Setbacks are normal and to be expected and will sometimes necessitate the use of extra medications or steps until the allergic reaction can be brought under control again

If you're uncertain if the symptoms your cat is displaying could be from allergies, speak to a vet so you can discuss your cat’s symptoms and possible treatments.


Reviewed and fact-checked by

Dr. Mari, DVM at Pawp

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