My dog developed skin allergy in last spring, and and she kept licking her belly and had severe hair loss there. We tried quite a few shampoos, body washes, and the Vet recommended Benadryl. None of them really helped. We kept trying until one day we found Zesty Paws Allergy Immune Supplement for Dogs.
It is a grain free chew and contains LOTS of ingredients including colostrum (pre milk), vitamins, antioxidants, prebiotics and probiotics…. I fed my medium sized dog two chews a day, and surprisingly, she stopped licking and the losing hair grew back after a few weeks.
I am not sure which ingredient worked, or if it will work for other type of allergies. Amazon has more than 15,000 reviews on this product with a average rating 4.3 out of 5 as of today.