My dog need a medication

I agree with barb's answer. Need to take him to the vet. Some dogs are allergic to flea bites. One of my dogs is, and he turns bright red, and itches non stop. He has to get a cortizone shot for it. Could also be regular allergies to grass, pollen, molds as well. My mom's dogs were getting bad rash/hot spots, losing hair, it was their food-too much protein in it for them. Her cat had rashes and bald spots, ended up being from worms. Could also be mange-which is transmittable to humans. So, could be lots of things, best to have the vet diagnose it for proper treatment. Good luck!!