Possible allergy?

Question
Hello Dr. Gotthelf,

I found you by doing some research on my cat. He is displaying some unusual behavior such as avoiding the floor and vacant stares. He also has some physical symptoms including rash and balding. So far I have found information on psychogenic alopecia as well as a possible allergy. There was a question you answered that matches my exact problem. Here is the link...
http://en.allexperts.com/q/Ask-Veterinarian-700/Fleas-m.htm#b

We don't believe it is fleas since we can't find any on him or in the house. We gave him advantage but nothing changed. We took him to the vet to be sure and she ruled out fleas and mites. She did give him a steroid shot, but unfortunately, it did nothing. He is still obsessively scratching and licking and avoiding the floor. He rarely sleeps and is always alert. He does still have an appetite and will only stay on the floor long enough to eat or rush to the litter box. We have had no changes to our house, other than a Christmas tree over the holiday. Could he be allergic to that? If so, wouldn't the steroid help?

I'm completely lost and upset over this. It would be so helpful to get a second opinion. Thank you.

Sincerely,
Kat

Answer
Sometimes an antihistamine will help an allergic cat and sometimes cats have an abnormal behavior that makes them scratch obsessively.  Do you know if the vet used DepoMedrol as the steroid? Another option is to use a drug called ATOPICA for cats.  If nothing seems to help, you may need to see a specialist in veterinary dermatology in your area.