Derm/feline

Question
I have a large(16lb) cream colored, 9 year old taby cat. Over the last few years (5)he has had areas of open skin,mostly on his hind legs and belly. He eats away at these areas until there is no hair and the areas are red and open. Initially I had read that cats have hot spots and perhaps he had allergies. I treated with a cortisone spay which does seem to help with the itching. This year though he had the spots all summer, which did not happen in previous years, which at the time lead me to believe the allergies were seasonal. Last night I noticed a spot of red scabbiness on the top of his head, an area he couldn't have self inflicted. Does this dermatology issue warrant a trip to the vet, which is always very traumatic or is there something I can do for him at home?

Answer
If it is an allergy, the best ttreatment is frequent baths, which most cats will not allow.  Sometimes daily wipes with a wet washcloth will work.  Having said that, there is a shot of cortisone that cats tolerate really well and it is given once a month or so.  It is called DepoMedrol and it gives cats long term relief from the itching that goes along with allergies.