Atopic Dermatitis in Cats

The allergens the cat reacts to can vary widely from outdoor allergens to fabrics, rubber, and even house dust. The lesions on the cat’s body can be clustered on its face, trunk, and anus. What looks just like acne on the cat’s chin may actually be signs of a skin reaction to an allergen.

Atopic dermatitis is a skin reaction to an allergen a cat has inhaled or touched, such as pollen. As it reacts to the allergen, the cat’s skin breaks out and begins itching. When the cat scratches the itchy hot spots, it does so often enough that the skin is broken, beginning to bleed and even developing signs of infection.

Some of the cat’s symptoms will be easily recognizable, since humans also develop the same symptoms with an allergic reaction. Other symptoms will be unique to cats:

• Miliary dermatitis or crusty bumps
• Eosinophilic plaques or irritated hot spots on the skin
• Scratched, mutilated skin
• Thin, long, red lesions or linear granulomas
• Skin appears to twitch
• Cat pulls tufts of hair out of the skin
• Waxy otitis or skin irritation with or without infection (in the ears)
• Chin acne
• Alopecia or hair loss
• Cat paws its face
• Evidence of excessive licking (behind the legs, on the back and stomach)
• Bad skin odor
• Thickened areas of skin that have changed color
• Scaly, crusty skin

As with the list of symptoms of atopic dermatitis, the causes are wide-ranging as well:

• House dust, dust mites
• Trees
• Weed pollens
• Grass and grass pollens
• Flea bites
• Wool or nylon
• Plastic or rubber
• Foods and additives, such as grains, individual meats, or food coloring
• Milk products
• Mold spores
• Insect proteins

Other factors make a cat more vulnerable as well:

• Genetic predisposition: symptoms develop after several exposures to an allergen.
• Cats with all-over orange (ginger) fur or orange in their coloration (calico and tortoise-shell)
• Purebred cats are more likely to develop atopic dermatitis 
• Geographic factors such as different plants and pollens
• Endocrine diseases

Vets easily recognize allergic reactions, but they will run diagnostic tests to make sure the diagnosis is correct. After giving the cat a full physical, the vet tests for atopic dermatitis (AD) by eliminating potential allergens from the cat’s environment until the offending item is detected and isolated. This method is most often used when the vet suspects a food allergy.

As the exam is in progress, the vet makes note of any clinical signs of atopy, such as skin lesions or sores from excessive scratching or biting. The cat is also examined for otitis, either waxy or without infection.

The vet asks the cat’s owner several questions, including whether the cat is allowed to go outdoors and if there are several pets in the home. If there are, the vet asks if the other pets are experiencing skin problems as well. The vet also asks whether the cat’s symptoms happen year-round or if they are seasonal. Finally, the vet asks if the cat is responsive to steroids. Blood is drawn from the cat to look for antibodies.

If the vet is fairly sure the cat has AD, the next step is allergy testing. This is done through blood tests or by inserting a suspected allergen into the skin (intradermal testing). No exam is complete without the vet taking skin scrapings or combing the cat’s skin and fur for fleas. The vet also takes fungal cultures to make sure the cat hasn’t developed a fungal infection.

Avoidance

The first thing the vet recommends is avoidance. As the cat is undergoing treatments, it’s vital that the substances to which it is allergic not be allowed back into its system. Depending on what the cat is allergic to, the owner will have to take several strategies. 

If the cat is allergic to molds, it will need to be kept away from basements and off the lawn after mowing. Humidifiers should be cleaned and disinfected after every use. Dehumidifiers should be used regularly to keep humidity from building up. Pet foods shouldn’t be allowed to sit, gathering dust. Houseplants should be kept to a minimum or eliminated, as standing water is the perfect medium for developing mold.

If the cat is allergic to house dust, furnace filters should be regularly changed, just as they are for asthmatic humans. The cat should be kept out of rooms that have just been vacuumed.

For any pollen allergies, the cat should be rinsed off after coming in from outdoors, especially if it has spent time in weeds or grass. When pollen counts are especially high, the cat should be kept inside. Rather than opening windows, the cat’s owner should use an air conditioner.

Therapies

Medications can be divided into topical, injectable and oral. Topical medications include anti-itch remedies, rinses and shampoos. Their relief isn’t long-term. Hydrocortisone shampoos and shampoos with colloidal oatmeal may also offer temporary relief.

Allergic cats benefit from Omega-3 fatty acids added to their foods or as skin supplements. These should be used regularly to ensure the cat responds and gets relief. Omega-6 fatty acids can make allergic reactions worse, so stick to Omega-3.

Antihistamines such as Chlorpheniramine, Diphenhydramine, Hydroxyzine and Clementine fumarate can reduce the cat’s histamine response to allergens. Not every cat responds to every antihistamine, so vets and cat owners will need to try different ones until they find the right medication.

These medications come with potential side effects, which include dry mouth, diarrhea, lethargy and sedation.

Cyclosporine, if given to the cat for three to four weeks, may help alleviate seasonal allergies. Injectable and oral steroids are extremely helpful for severe inflammation and itching. These should be used short-term because of their side effects, especially if they aren’t used correctly.

If the cat has developed yeast or bacterial skin infections, these have to be treated with antifungal medication or an antibiotic.

Once the cat has been diagnosed with atopic dermatitis, treatment allows it to resume a good quality of life. To prevent future outbreaks, the cat’s owners will need to help the cat avoid every identified allergen for the rest of its life. If the cat’s allergies include weed, tree and grass pollen, they may need to train the cat to stay indoors.

For cats with seasonal allergy outbreaks, medications and prescriptions are easily obtainable, allowing the owners to give the cat relief from the misery of hot spots, itching, scratching and potential skin infections. As long as dosing instructions are followed, the cat will benefit, especially if it needs to be on medications long-term. Corticosteroidal medications can have significant side effects, so these should only be given to the cat for as long as prescribed, then discontinued.