Hi,
Welcome to the ehealthforum and I am really glad to help you out.
It can be due to dermatitis skin. First of all, do not use any cosmetic products at the site. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments. Application of mild corticosteroid cream and oral antiinflammatories like ibuprofen/acetaminophen are also helpful, but you need to get a doctorâs prescription before taking these medicines.
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, you are requested to consult your doctor. I sincerely hope that helps. Take care.