Cats can develop allergies to molds, pollen, plants, grass or trees indigenous to a specific part of the country. Ask your veterinarian to take a blood sample and submit it to a veterinary lab specializing in allergy testing by the RAST method, which are regionalized to screen for agents localized to various areas in the country. Once the allergy is determined, an individualized set of injectible antigens can be created specifically for your cat. In the interim, try one milligram per pound of body weight of Benadryl three times daily in the tablet form. Sometimes a half tablet of Chlortrimeton twice daily will work better. These should take the edge off the itching and allow steroids to be used only during a crisis.