Just like people, pets can develop allergies to the things they touch, eat and breathe in. Substances that trigger an allergy are known as allergens. But it can be remarkably difficult to determine exactly what your cat is allergic to!

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Signs that your cat may have an allergy include:

  • Scratching.
  • Excessive licking (grooming).
  • Red, scabby, or dry skin.
  • Sneezing, coughing, and wheezing.
  • Itchy runny eyes.
  • Ear infections.
  • Vomiting or diarrhoea.
  • Swollen, sensitive paws.

Your vet may recommend allergy testing to try to find out the cause of the allergic reaction. There are three types of allergy tests for cats – skin testing, blood testing and food trials. 

The usual suspects

Before getting into the nitty gritty on the different types of allergy tests on offer, it’s worth discussing the likely causes of allergies in cats. 

Flea allergies

There are other skin parasites your vet may also want to rule out, but fleas are by far the most common cause of allergic skin disease in cats. Flea allergy is caused by the flea’s saliva, and it only takes a few bites to cause a problem. You can find out more about how to control fleas in your cat here: Cats Protection – flea advice. More information about flea allergies can also be found here: PDSA – flea allergy in cats. 

Environmental allergies

Pollen, grass, fungi, mould, and dust can trigger allergies in cats. Cats can also react to cigarette smoke, perfumes and some cleaning products. ‘Atopic dermatitis’ is a term used by vets to describe allergies caused by commonplace and otherwise harmless substances. There is often a genetic or inherited predisposition to developing this type of allergic reaction. 

Food allergies

Food allergies can cause gut issues like sickness and diarrhoea, but sometimes food allergies cause itchy skin. Cats are usually allergic to a particular protein in food, although carbohydrates, preservatives and certain food dyes can also play a part.

Further information about atopic dermatitis and food allergies can be found here: International Cat Care – Itchy cat, when it’s not fleas 

Why test for allergies?

Allergy testing is not a test to determine if your cat has allergies or not. Testing is done to assess the body’s reaction to allergens to determine what substances would be best to avoid and, if appropriate, what substances would make the best ingredients for an allergy ‘vaccine’ or hyposensitisation serum to help decrease your cat’s sensitivity.

It’s important to know that an allergy is not something that can ever be cured completely. The aim is to remove the trigger, and when this is not possible, the goal is to manage the symptoms of the allergy to a level that is acceptable for your cat to live with. 

Skin testing

For skin testing, referral to a veterinary dermatologist is needed. Your cat will need to stop any anti-itch medications for a while ahead of the test. Sedation for the procedure is often best, to reduce any stress they may experience. An area of skin is shaved, and a grid of dots drawn on the skin to mark where the allergens go. Then small amounts of allergens are injected into the skin. After several minutes, the reactions in the skin are graded by measuring the amount of localised swelling. The allergens creating the strongest reactions can then be identified. 

Blood testing

Your vet will take a blood sample and send it to a laboratory for analysis. In general, it is not necessary to withhold anti-itch medications, and your cat won’t usually need to be sedated. The laboratory tests the blood for the types of ‘antibodies’ (proteins created by the immune system) that generate allergy symptoms. These are known as IgE antibodies.  Substances that have generated the highest amounts of IgE are identified as the potential cause of the allergy.

What about tests for food allergy?

Blood and skin tests are not useful tests for identifying the cause of a food allergy in cats. The best method of diagnosing a food allergy is by feeding your cat a hypoallergenic diet for a period of several weeks. This is known as a ‘food trial’. If the allergy signs resolve, a food challenge is performed by feeding your cat’s old diet again. If the signs of allergy return, a diagnosis of food allergy is confirmed.

More information about food allergy in cats can be found here: PDSA – food allergy in cats. 

Many dermatologists perform both skin and blood tests on patients to decide what allergens should be included in an allergy vaccine. Some specialists feel the skin test is best and certainly the skin test is traditional. Others feel strongly about the blood tests, and blood tests are less invasive for a cat to undergo. You might think that either test should produce the same results, but this is rarely the case! These tests may not always pinpoint the cause of the allergy, but in around 75% of patients they are reliable, if interpreted carefully by an expert.

A word on allergy vaccines

Hyposensitising injections, commonly known as allergy vaccines, can be created specifically for your cat by specialist laboratories. When allergy tests have been used to identify what allergens are causing the allergy, injections can be created to regularly expose your cat to small amounts of the allergen. This desensitises the immune system and reduces the signs of allergy. Hyposensitising injections are not curative, can be expensive, can take up to a year before any effect is seen, and may not work in every case. However, they can also reduce the need for other medications to keep an allergy under control.

Can you avoid allergy testing your cat altogether?

Allergy testing is expensive, and it is not always possible to avoid some of the allergens that the testing may identify. It’s cost effective to start with strict flea control and a hypoallergenic diet to see if the signs of allergy resolve. 

Anti-allergy medications do not cure allergies but can help decrease the symptoms. Steroids are relatively cheap and can control allergies very effectively without allergy testing, especially if used alongside effective flea control. However, long-term use of steroids can result in health problems such as weight gain, diabetes, and an increased risk of infection. For some at-risk cats, steroids cannot be used, but generally cats tend to be more resilient than dogs when it comes to steroid side effects.

It’s important to know that without addressing the underlying cause of the allergy, the symptoms will return when medication is stopped.

Allergy testing in cats – is it worth it?

For many cats, allergies can be controlled with strict flea control, a hypoallergenic diet and medication without the need for allergy testing. However, some cats can experience side effects to medication or may not respond adequately. Poorly controlled allergies can have a serious impact on quality of life. If this is the case for your cat, talk to your vet about allergy testing. Allergy testing may result in a reduced need for medications and enable your vet to use more specific and targeted allergy treatments.

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