What Causes Folliculitis In Chest, Arms And Legs?

Hello, My son has just broken out with what Doctors seem to think is Folliculitis. It started in the back about a week ago then spread to chest, arms and legs. He was on Clindahexal and did not respond. Now on amoxicillin and a fungal oral tablet. Still seem no response. Old outbreaks are healing but new ones appear.