My Siamese Cat Is Constantly Itching

Q: I have a male Siamese cat who is about 10 years old. He does not have fleas, as my female would probably have them, too. He scratches, and has small scabs and scratches his hair right out. His vet gave him a shot that stopped him for a few weeks, but now it seems to be worse than ever. What could be causing it?

A: I suspect your cat has allergies. The most common types of allergies in cats are flea allergy, food allergy and atopy (allergic inhalant dermatitis). 

Most cats with flea allergy have visible fleas, but not always. Cats with flea allergic dermatitis can show intense itching from only one or two flea bites.

Food allergy is another common cause of itching in cats, especially if the itching is around the head and face. A diagnosis of food allergy can be achieved by feeding your cat a hypoallergenic diet. This is a diet that contains a protein source that your cat has not been exposed to.  A few companies manufacture diets for this purpose. Hill’s, for example, has diets in which the primary protein source is venison or duck. Be aware that it can take up to 12 weeks to see a response.

Cats with atopy are allergic to something they inhale in their environment.  In some cases, it is seasonal, such as a plant pollen that appears at certain times of the year. In other cases, it can be year round, for example, in cats that are allergic to house dust mites.

I suspect your cat has atopy, because he responded to an injection given by your vet and it sounds like you've ruled out fleas. The injection was probably an anti-inflammatory drug (a corticosteroid). Food allergy often responds poorly to corticosteroids, but atopy and flea-allergy respond dramatically. 

To be thorough, I’d treat your cats with a dose of one of the common monthly topical flea control products, to rule out flea allergy. Your cat may ultimately need to be treated again with anti-inflammatory medication. However, rather than give an injection, you vet should prescribe this medication in pill form, so that you can gradually taper to the lowest dose that controls the itching. Ideally, this would be administered every other day. You should also consider giving a supplement rich in omega-3 fatty acids, as they are also have anti-inflammatory effects in the skin.