This involves taking a tiny bit of the allergen that's causing him the trouble and injecting it into his skin. These allergens come in prepared solutions, so your vet can select the allergen to which your cat reacts. Oddly enough, this over stimulates the immune system so it no longer reacts to the allergen. Fatty acid supplements, antihistamines, and corticosteroids are all efficacious in allergy treatment for healthy young cats, but these may be contraindicated for older cats with health problems, or if you find it difficult to give your cat pills. Your vet will determine the best treatment for your cats itches, perhaps prescribing oral or injected corticosteroids to stop itching and discomfort.
Antihistamines seem effective in some cats.
Thus although cats suffer from allergic discomfort, treatments and medications can make your cat more comfortable and keep the allergy under control.