Hello,
I cannot confirm anything without examination but it can be contact dermatitis, allergy, sweat dermatitis, heat rash, insect or scabies bites, hives, eczema or viral rash. You can take over the counter antihistaminic like Benadryl or Claritin for itching. Application of calamine lotion is also soothing. If symptoms persist then please consult your doctor.
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.
He takes a Benadryl and goes to sleep. That suggests it may be an allergy. I have allergies. When I don't take an antihistamine I itch - not rash - ho hives - just an itch.