Hello,
It can be due to dermatitis skin or eczema. Wash the area with fresh water. Do not use any cosmetic products at the sites. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments. Maintain hygiene and try to keep the area clean and dry, wear loose-fitting cotton clothing. Also use mild soap like dove. Avoid deodorant / cosmetics. If the symptoms persist then get a KOH examination of the skin scrapings done from a dermatologist to rule out any fungal infection.
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 and please do keep me posted on how you are doing.
Try dermasil it will help