Common Cat Allergies

Allergies are not just a human problem, and an increasing number of domestic animals seem to be developing their own intolerances.

What is an allergic reaction?

An allergic reaction is the body’s way of responding to a foreign substance. It could be something your pet has touched, such as a type of plant, or it could be something she has ingested. When this foreign substance, referred to as an antigen, is detected by her body it triggers her immune system to immediately fight it, even if it isn’t something that is harmful.

An allergy is essentially the body fighting against something that it shouldn’t. It produces histamine and other chemicals which trigger the allergy symptoms.

Types of allergy in cats

There are four causes of allergies in cats. These are insect, food, inhalant and contact allergies. Each may present differently and will require specific treatment in order to make your cat comfortable again.

Insect Allergies

Flea allergy dermatitis is the most common cause of insect allergy in cats. The allergy is caused by flea saliva which reacts with the skin when your cat becomes bitten.

Symptoms of insect allergy in cats

  • Scratching and itching

  • Red, crusty lumps around the head, neck and back which your cat may scratch relentlessly at

  • Licking of the fur, especially around the thighs and base of the tail

  • Hair loss from excessive scratching

Treating insect allergies in cats

Unless you can visibly see fleas or other insects in your cat’s fur, you may need to take her to your veterinarian to obtain a diagnosis.

The first step is to remove the infestation from your pet, which can be done using various topical treatments. You will also need to ensure that any insects in your home are also dealt with using the necessary treatments and preventatives.

If your cat has been biting and scratching her skin, she may have developed an infection which requires a course of antibiotics, or topical medicated creams or shampoos. Your vet will be able to prescribe the right treatment based on your cat’s needs.

Your vet may also prescribe your pet some antihistamines or steroids to help reduce inflammation and calm the itch.

Food Allergies

Cats, like humans, can be allergic to the things that they eat or one of the ingredients within something that they have eaten. The most common causes of food allergies in cats are beef, fish, eggs and wheat.

Symptoms of food allergy in cats

  • Vomiting

  • Diarrhea

  • Itching the face, neck, ears, head and abdomen

  • Swollen or infected ears

  • Hair loss from excessive scratching

Treating food allergies in cats

In order to successfully diagnose a food allergy your veterinarian will have to place your cat on a food trial. This usually lasts around 8 to 12 weeks and during this time you must not allow your cat to deviate from the prescribed diet in any way. If the allergy disappears after the trial then your vet can be pretty certain that food was the cause. The way each veterinarian reintroduces food to determine the cause of the allergy varies, but you will be given precise instructions to follow. Again, you should not deviate from these instructions as it could invalidate the results of the testing.

Once your vet has established the cause of your cat’s food allergy, you will need to avoid this product and any products that contain it as an ingredient.

Inhalant Allergy

This type of allergy arises from breathing in pollen, mould, dust mites and other allergens that are in your cat’s environment. Symptoms can be seasonal or present all year round.

Symptoms of inhalant allergy in cats

  • Red, crusty rash around the head, neck and back which cause persistent itching

  • Scabby lesions

  • Watery, sore eyes

  • Intense itching and scratching

  • Hair loss, usually as a result of scratching

Treating inhalant allergies in cats

To diagnose inhalant allergies, it will be necessary for your vet to rule out any other possible causes of the symptoms. This may involve asking you for a concise medical history of your pet, taking skin scrapings and performing intradermal skin tests and giving your cat a blood test.

Treatment will depend on the cause of the allergy, but may include corticosteroids which will help to relieve the symptoms although it won’t cure your cat of the condition. Avoiding the cause of the allergy is the best course of action wherever possible.

Contact Allergy

This is the least common type of allergy and requires your cat to come into a substance that causes her body to make an autoimmune response.

Symptoms of contact allergy in cats

  • Inflammation of the skin

  • Redness of the skin

  • Intense itching, particularly of the chin, ears, toes, underbelly and anus

  • Skin lesions

  • Thickening of the skin or a change in texture

Treating contact allergies in cats

A physical examination is the first step that your vet will take to try and determine the cause of your cat’s symptoms, and to rule out any other possible reasons for them. Your vet may also choose to perform a patch test or skin biopsy to help to determine the cause of the reaction.


If your cat is suffering from symptoms relating to an allergic reaction, seek advice from Family Pet Hospital or your local veternarian so that you can get your cat feeling happy and healthy again.