Q: My teenage son just had a round rash show up on his shoulder. What should we do about it?
A: It sound like it could be ringworm, which is a common fungal skin infection. It is not actually caused by a worm invading the body. It usually can be treated by applying OTC clotrimazole cream for several days. More widespread infections may require prescription oral medications and a visit to a physician. Try to prevent it in the future by keeping cool, clean, and dry as much as possible. Also avoid infected animals and do not share personal items like towels or hairbrushes.