What kind of dog is he? My dog is a golden retriever, and although she has never had a huge flea problem ( I don't think ever) her skin is really sensitive, and if we are not feeding her special types of food, she will scratch until she can't scratch anymore. All those chiggers probably made her skin really sensitive, especially as a puppy. I would take her to the vet, and see if they say anything about it. But maybe I would mix in a bit of sensitive skin dog food with her puppy food, and see if that helps. My dog eats a venicin mix, which isn't as expensive as it sounds. Good luck!