You would need to see a skin specialist to rule out sunburn, heat rash
or miliaria, eczema, sweat dermatitis, heat rash
, acne, folliculitis, impetigo, even lupus, etc.
You could take some oral antihistamine or antiallergic medications like loratadine or cetrizine and see if it helps with your symptoms. Apply calamine lotion at the site of the lesions to help soothe the itching.
What other symptoms are you having? Since when have you noticed the leions?