Welcome to healthcare magic.
From your description, it seems to me that your son may be having scabies
It is an infestation by a mite which causes intense itching worse at night and small, reddish rashes between the fingers, underarms, around the belly button, buttocks and groins. It is contagious. You may have lesions only in limited areas also.
All your family members need to take treatment simultaneously and also your son' s friends. It is treated by a single application of 5% permethrin cream
overnight. He could also take an antihistamine to relieve itching.
Hope this helps you.