Feline Skin Allergies by Dr. Destinee Dummer

“My cat won’t stop scratching! She is obsessed with grooming herself, her hair is falling out and she has these small red bumps all over her skin!” … If parasites have been ruled out, sounds like this cat may be suffering from allergies.

The most common cause for itchy skin in the cat is a sensitivity to flea bites, “flea allergic dermatitis”, or FAD. Not only are the fleas themselves irritating to the cat, the flea allergic cat will have a persistent itch after just one bite from a flea, much like a person who is allergic to mosquito bites.

Lucky for us in Calgary, fleas are uncommon and thus a less likely cause of skin problems for our feline friends.
The second most common reason for itchy skin (pruritis) in your pet is atopy, otherwise known as sensitivity to environmental allergens, or ‘inhalant allergic dermatitis”. Common allergens include: house dust, house dust mites, molds, human dander, feathers, weeds, pollens, grasses and trees.

This disease complex generally begins at a young age (6mos-2yrs) and can initially appear seasonal, especially if pollen and grass are inciting factors, however, 80% of cases can become year round. Your cat will be extremely itchy and lesions may be localized to the face, neck and parts of the ears. Not only will the constant scratching cause wounds on the skin, you may notice areas where the hair has fallen out (alopecia) or there are raised white bumps not unlike pimples. Left untreated, the skin can become moist with the pruritis further exacerbated by bacteria and yeast causing secondary infections.

Diagnosis is usually made by elimination – this means your veterinarian will want to run a few tests to ensure there is not another explanation for the lesions and pruritis being seen, like mites, dermatophytes, food allergies or parasites.

Treatment often involves lifelong medications if avoidance of the particular allergen is impossible. Antihistamines and anti-inflammatories are the mainstay, but immune modulators can also be used in resistant cases. Antibiotics may also be required to treat secondary bacterial infections that may arise. Supplementing your cat’s diet with fatty acids can make a big difference if medications alone are not effective.

Hyposensitization (creating specific vaccines to de-sensitize your cat’s reactions to a specific allergen) is effective in 50-80% of cases. This is a suitable treatment option if the allergens can be identified through skin or blood testing. Unfortunately, many atopic cats have concurrent allergies such as FAD or food allergies, making hyposensitization less useful.

Food allergies comprise the 3rd most common type of allergy cats can experience. The lesions can be similar to atopic cats with itchy skin around the face, necks and ears, but is usually non-seasonal, may include  GI upset (vomiting and diarrhea) and can present at any age.

Cats most commonly are allergic to protein – beef, chicken, corn, wheat, cows milk, soy, eggs – and they typically develop allergies to the food they have been extensively exposed to. This means your cat can suddenly become allergic to the food it has been eating for the past 5 years.

The diagnosis is made by running a food trial. The idea is to feed a diet which eliminates the protein causing the allergy for 6-8 weeks looking for cessation of symptoms. This can become quite tricky when food labels list ingredients using unfamiliar words that describe the same product. You may think you are avoiding a particular protein when it has just been listed under a different name. For this reason, an elimination food trial should be done under the guidance of your veterinarian! During the food trial, no treats or flavoured medications should be given. At the end of the food trial, the original food is re-presented and symptoms generally return within days.

Once the allergen(s) has been identified, your veterinarian will work with you to find a complete balanced diet your pet can eat and live a happy symptom free lifestyle.

Lastly, contact hyper sensitivities are very rare skin reactions to topical medications, plants, plastic food dishes, etc. Lesions are generally localized to the area that come into contact with the allergen, such as the tummy or foot pads. Avoidance of the particular allergen is paramount in treating these cases. For example, chin acne can be controlled by using stainless steel food and water dishes that are cleaned regularly.