Retreiver skin problems/vomiting

Question
Ben is my 3yr old Golden Retreiver.  About a month ago he had rash and itching, particularily stomach/groin area.  His scratching resulted in infection which was treated with antibiotics, symptoms cleared.  My vet gave me some prednisone to use, but I didn't like the side effects so only gave one pill.
Now, the skin redness is back full force with itching.  He vomited 3x during the night. He is off his food but drinking water.  
I did give a prednisone last night even though I feel this may not be the answer.
Thanks for any advice/input.
Sue Grattan
PS.we live in MN, I had thought the winter dryness may affect him.  Maybe dogfood?  He eats Kibbles & Bits dry food.

Answer
I would definitely switch him to a better quality food as he may have a food allergy.  Fish-based diets, in my opinion, work best for the skin.  Verus, Flint River Ranch and Wellness are three very good brands.

I would also get him started on Ester C at a dose of 10 mg per pound twice a day, Fish Oil 1000 mg a day, plain yogurt and digestive enzymes such as Dancing Paws Shake'NZyme.

You can try Benadryl at a dose of 1-2 mg per pound 2-3 X a day to see if that helps the itching...prednisone does have a lot of side effects, but as a short term use it okay.