Cat Skin Allergies

By Emily A. Fassbaugh, DVM on Feb. 2, 2021

Cats, just like dogs, can suffer from skin disease caused by allergies. Cat skin allergies can cause profound itching and pain in cats.

Finding the source of the allergy is fundamental to helping your cat’s skin heal and relieving their discomfort. And once the source of the allergy is found, it is important to continue to manage your cat’s allergy to help prevent the skin disease from returning.

Signs of a Skin Allergy in Cats

The most common signs of cat skin allergies are:

Hair loss
Scabs
Ulcers and open sores
Intense itchiness, which will appear as frequent scratching or overgrooming

Sometimes cats will also have ear infections, so they may scratch their ears a lot, have black debris in the ears, or shake their head. These cats will sometimes be extremely uncomfortable or in pain. Their skin may twitch, or they might hiss, growl, or move away when you pet them or try to pet them.

What Causes Cat Skin Allergies?

An allergy at its root is caused by the immune system reacting inappropriately to things that are not viruses or bacteria. When your cat has an allergy, their immune system thinks that a benign protein is a virus or parasite trying to attack it, which causes inflammation.

There are three triggers for skin allergies in cats:

Many cats that go to the veterinarian for skin problems may have mites or ringworm fungus as a cause for their disease, so your veterinarian may recommend testing to rule these out.

Many cats also have bacterial infections on their skin from constantly damaging the skin, which will slow healing. Your veterinarian may recommend testing for infection and if so, will treat your cat with antibiotics.

Cat Flea Allergy Dermatitis

A flea allergy is triggered by a reaction to a flea’s saliva. Cats who live exclusively indoors are just as susceptible to fleas as cats who go outside because fleas can live anywhere in the environment.

If you are currently using flea prevention on your cat and your veterinarian can’t find any sign of fleas, that would suggest that your cat has an allergy to a food or something in the environment.

Cat Food Allergies

Most food-allergic cats are allergic to the protein in the food, not the grain source. This means that corn and wheat aren’t typically a problem for cats. The most common food allergies in cats are to chicken and fish.

Environmental Allergies

Environmental allergies are commonly triggered by pollens, molds, dust spores, and dander. These are all substances that can be found on the ground and in the air. We commonly call an allergy to substances in the environment “atopic dermatitis.”

How Do You Treat Cat Dermatitis?

Treating cat skin allergies involves several steps: relieving itchiness, reducing inflammation, treating bacterial infections, and finding the cause.

Reduce the Inflammation and Soothe the Itch

All cats that suffer from allergic skin disease are very itchy. At the first visit, your veterinarian may prescribe corticosteroids, such as prednisone, to alleviate the itch and inflammation in the skin.

For all skin diseases, bathing your cat can help to reduce inflammation and soothe their skin. Since most cats don’t like baths, you may want to try a product like a mousse or a dry shampoo for cats that can clean your cat while avoiding water. Ask your veterinarian to recommend the right product for your cat.

Treat Bacterial Infections

Many cats also suffer from secondary bacterial infections, so they will often receive antibiotics to treat the infection. Your veterinarian may also recommend putting an Elizabethan collar on your cat to prevent them from scratching their face or overgrooming.

Find the Cause of Your Cat’s Skin Allergies

If you only treat the itching, scabs, and infections without knowing what caused your cat’s skin allergies, you will end up back at the vet’s office again. Finding out the cause and then treating the underlying condition is the key to breaking the cycle.

How Does Your Vet Determine the Cause of Your Cat’s Skin Allergies?

It is important to note that figuring out the cause of your cat’s skin allergy will require multiple visits to your veterinarian. Typically, your veterinarian will want to see your cat every two to three weeks until your cat gets better. These are the steps your vet will take to determine why your cat has skin allergies.

Checking for Signs of Flea Allergies

Flea allergies are quite common for cats. Your veterinarian will check your cat for fleas at the appointment. Interestingly, because allergic cats overgroom, they may remove all or most of the fleas present, so your veterinarian might not see any fleas on your cat. But just because fleas are not seen does not mean they are not the cause for your cat’s skin disease.

Your veterinarian will ask if you are using monthly flea prevention. If you are not, they will recommend a product that you will apply to your cat’s skin monthly. Using an effective flea prevention and assessing your cat’s response to it will help to figure out if your cat is allergic to fleas.

It is especially important to use a veterinarian-recommended flea prevention every month to control fleas. This will not only treat and prevent a cat’s flea allergies, but it will also reduce any itching caused by fleas.

Testing for Cat Food Allergies

If your cat is still itchy after treating their infection and using a monthly flea preventive, the next step is to test for a food allergy. Unlike people, there is no blood test for food allergies in cats. To figure out if your cat has an allergy to food, your veterinarian will prescribe either a novel protein diet or a hypoallergenic diet.

A novel protein diet is one with a protein source that your cat has never had before. Venison, rabbit, and duck are common novel protein sources.
A hypoallergenic diet is a food in which the protein source is broken down into small molecular pieces so that the body can no longer recognize it as a protein. Think of a puzzle that has an image of a pirate ship. When you take the puzzle apart, you can no longer see the pirate ship.

To diagnose a food allergy, your cat will need to be on the prescribed diet for a minimum of two months without eating anything but that diet. If the diet trial is effective, the next step is to add a new protein source to the food for one to two weeks.

If there is no reaction, we can assume that protein is not causing the allergy; if there is a reaction, we know that your cat is allergic to that protein and it must be avoided. Occasionally, some cats must stay on the prescription diet for life to manage their food allergy.

Managing Atopic Dermatitis in Cats

Atopic dermatitis (environmental allergies) is a diagnosis of exclusion. This means that your cat has consistently been on flea preventatives, has completed a food trial, and is still very itchy. At this point, the treatment options include:

Continuing to use corticosteroids
Using an immunomodulatory medication like Atopica
Blood testing for allergies to start immunotherapy (allergy shots)

Corticosteroids

Corticosteroids are anti-inflammatories, which means that they reduce the inflammation associated with cat skin allergies. Commonly used corticosteroids are prednisolone and triamcinolone.

Possible side effects include increased thirst and kidney injury. In cats, corticosteroids are usually quite safe, but they must be used at a dose that is as low as possible while still controlling your cat’s skin disease.

Atopica

Atopica, also called cyclosporine, suppresses the immune system cells that are associated with allergies so there is less inflammation. Possible side effects of cyclosporine are stomach upset and diarrhea, but it is generally considered safe in cats.

Allergy Shots

The final possibility for atopic dermatitis is immunotherapy, or allergy shots. Immunotherapy means that we are trying to change how the immune system sees the antigens (the proteins that cause an immune reaction) so that it no longer reacts.

This starts with a blood or skin test to figure out exactly what environmental antigens your cat is reacting to. Once the test has shown what your cat is allergic too, a laboratory makes a serum of the antigens.

You will give your cat an allergy shot several times a week. The goal is to vaccinate your cat against the antigens that your cat is reacting to. Immunotherapy takes about one year to see how effective the therapy will be.

It is important to note that there are no cures for allergic skin disease, and that many cats have multiple allergies. All therapies associated with allergies in cats are meant to control and manage the amount of inflammation caused by the allergy, as well as prevent infections and discomfort.

Featured image: iStock.com/sony_moon