Hello and thanks for your query. I shall make an effort to provide you with good professional recommendations specific to your questions. This rash on buttocks can be due to ringworm, but the exact diagnosis had to be done. If it is a fungal infection, then you may need topical and oral antifungals. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, I request you to consult your dermatologist. Yet again, I duly appreciate your query to me, I do hope that have found something useful to help you and I shall be glad to answer any further apprehensions. Sincerely,