I would try a course of Lotrimin cream and treat as if it's ringworm.
Hello,
If the red skin is not itchy then it can be due to dermatitis skin as well. You need to get it examined from a dermatologist to confirm the diagnosis. Treatment is diagnosis specific.
You should also maintain hygiene and try to keep the area clean and dry, wear loose-fitting cotton clothing. Also use an antibacterial soap or mild soap like dove. Avoid deodorant / cosmetics. You can also use calamine lotion or cream with zinc oxide paste applied directly to wet skin after bathing.
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.