Basset Hound With a Rash on Belly?

My female Bassett hound has developed a rash all over her belly. It is the first year she has ever had this. She is eating the same food and drinking the same water. All of a sudden she has red blotches and bumps on her belly and under her little arms.

I took her to the vet and he said that he has had 10 other Bassett hounds like this but failed to know the answer. He was going to call a dermatologist for pets but I have not heard a response. I live in the deep south and the heat is very hot. I have tried everything: calamine lotion, triple antibiotic and others.

Does anyone a home remedy that is affective.

Thanks and help please,

Dar