There are many different causes of rashes on the skin and some of them do require medical evaluation and treatment. The doctors who would be best qualified to discuss this issue with you include your primary care doctor
and your dermatologist
. The most common cause of rashes under clothing is simply irritation of the skin. This can be causes by excessive sweating, or example. Often, simply keeping the skin dry and clean can clear things up. Occasionally, the rash can be a reaction to some chemical or some allergy. The most common causes are a new personal care product, soap, or laundry detergent. This would be more likely to give the symptoms you describe, where they do not seem to be related to the type of shirt. Fungal infections of the skin can also do this at times. If the rash does not clear up with simple measures, such as hygiene, changing detergents, and over the counter anti-itch creams, then your doctor may consider this possibility as well. As always, the diagnosis and the management of your particular skin condition will require a physical examination by your personal physician. Scheduling on office visit with your primary care doctor or your dermatologist is recommended if symptoms persist.