If the skin is redish pink on the belly then it's a skin problem. The vet told me to use Head and Shoulders dandruff shampoo (I used the Equate brand) to cure it. Works great. Medicated dog shampoo is good but dandruff shampoo is cheaper, milder for the skin, and smells better. My dog doesn't scratch now. The groomer said she has a lot of dogs that only use dandruff shampoo so she was fine with using it on my dog too.