Hello,
I cannot confirm anything without examination but it can be contact dermatitis, seborrheic dermatitis or eczema. Seborrheic dermatitis is usually caused by overgrowth of Malassezia furfur. This skin disease commonly affects adults, especially in warm and humid climates and is aggravated by sweating
and humidity. To confirm the diagnosis I would suggest you to get an evaluation done from a dermatologist.
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 dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.