Such a sad boy sitting at the window, waiting for mom to get home.

[TygrBright]

5. Siwsan, I'm gonna guess fungal or bacterial infection/exposure possible, but allergy likely.

And you probably want to minimize the steroid exposure, long-term side effects can be unpleasant for kittiboi (and you.) Coupla links:

Steroid Treatment - Effects in Cats
Side Effects Of Injectable and Oral Steroids In Cats

In a multi-cat household, fungal/bacterial pathogen identification can be somewhat easier - what (if anything) does he lick, lie/roll on, inhale or consume that the other kittehs do not lick/consume?

But allergen identification is harder with multiple kittehs, as you may need to feed him in isolation and/or prevent him from snitching the others' food/treats, while you do elimination diet trials.

Here's a good summary on cat allergies: Food Allergies in Cats

Also, do not forget to check possible environmental allergy triggers - I had one kittiboi who licked himself into an "Azerbaijani Poodle Cat" because (as we found out through much trial-and-error) he was exposed to a pine-based cleaning solution I used. Allergy triggers can be anywhere the kitteh is.

I'm not a vet, just a long-term kitteh parent who's seen several similar issues - of course you should always take a vet's advice first, but it doesn't hurt to gather information and be prepared with questions when you do see the vet!

helpfully,
Bright