Does your cat develop bald or scabby areas every year? Your cat may have an allergy – read more to find out what you can do and what to look out for!

With the weather warming up and the humid conditions we are finding more cats coming in with skin problems and in particular fleas.  Often people stop flea treatment over the summer not realizing that the winter temperatures in Auckland mean fleas can breed all winter and so numbers are slowly building up and then explode in the spring.

There are three types of allergy commonly seen in the cat: flea allergy dermatitis (by far the most common allergy), feline atopic dermatitis (an inherited tendency to display allergic symptoms after exposure to airborne allergens) and food allergy (a reaction by the animal's body to a particular food stuff). More rarely cats can be allergic to mosquito bites and we often see swollen and scabby noses as the weather gets warmer.

Flea allergy dermatitis occurs when the flea bites and the flea's saliva comes in contact with your cat's skin.

Common causes of feline atopic dermatitis include molds, dust mites, pollens (from trees, weeds and grasses) and feathers. These microscopic particles set up an allergic skin reaction in the sensitive individual. Depending on the particular allergy, the symptoms may be seasonal (pollens) or year round (house dust mites). With time, mild symptoms become more severe and continue for a longer period.

Food allergic cats develop a reaction to foods such as beef, fish, wheat or eggs or to chemical preservatives and food dye even though they have been eating the food for months or years!

What allergic symptoms will my cat have?

The major sign is itching and scratching. Cats also rub their faces and lick themselves (more than just grooming). Other signs are a result of scratching and licking: hair loss, redness, dandruff and small red crusts ("miliary dermatitis"). Ulcerated red raw areas may be seen on the belly, the back of the hind legs or around the head and neck.   In cats with food allergy, vomiting and/or diarrhea may be seen in addition to skin changes.

How do we diagnose the allergic cat?

Cats with flea allergy dermatitis respond to a thorough flea control program.  This is by far the most common with over 90% of the cats presented with skin problems having an allergy to flea saliva. 

The best way to identify atopic dermatitis is to perform a skin test. This involves sedating your cat, placing an intravenous catheter in a foreleg, clipping the side of the chest and pricking the skin with tiny amounts of purified allergen extracts. Reactions to the extract (swelling and redness) are observed over the next thirty minutes. This needs to be done by a skin specialist. In some cases, it may require waiting up to two months after all supportive medications have been stopped before a skin test can be performed. Often we use their response to antinflammatory medications to gauge if an allergy is likely.

Food allergy is diagnosed by feeding a type of food that has never, or rarely, been fed. If your pet is reacting to a food protein, an improvement in itchiness and/or vomiting should be seen in six to eight weeks. This can be difficult as they put a lot of different things you may not even realise in cat foods these days so talk to your vet about the most appropriate diet for your cat if you suspect they could have a food allergy.

Treatment

Flea control to treat flea allergy dermatitis must be maintained for the life of your cat. It may be necessary to treat the patient with supportive medication in addition to the flea control.. In case of a mild seasonal allergy (less than two months), antihistamines and steroids (which relieve the symptoms of the allergy) may be the treatment of choice. Cats reacting to ingredients due to food allergy must be fed a special diet that does not contain the allergic substance.