Hi,
This could be allergic reactions to unknown substances, skin hypersensitivity, eczema, dermatitis or insect/bug bites.
What is your age? Could you describe the rash a little?
Do you notice the lesions trigerred in response to a specific stimulus like insect bite?
You should try to keep the area dry and clean. Try some powder to absorb the sweat.
Apply calamine lotion at the site and take some oral antihistamine medications like loratadine or cetrizine for your complaints. You should wash all your linen and bed clothing once in an antibacterial solution and sun dry it.
If the symptoms are still persistent, consult your dermatologist and get a proper clinical evaluation done.
Let us know if you have any doubts and keep us posted on how you are doing.
Good luck.
Could it be spider or flea bites? Try not to scratch....could make it worse and become infected. Benadryl cream could bring it down?