My son (7 years old) has developed an itchy rash on his buttocks and upper area on his legs right under his buttocks. It is localized to this area. The rash is raised red bumps. They are itchy. There are probably anywhere from 20-30 of them. The raised bumps have redness around them. He is hypersensitive to bug bites. For example, mosquitos give him a lot of trouble during the summer. He has had no fever, no cough, etc. I have checked the beds for bed bugs, and I see none. We have bought him new underwear recently, but he does not have anything on the front in his genital area.