Hi,
This is probably a fungal infection which is called Tinea. Fungi thrive in warm, damp environments; therefore they are commonly seen in skin folds where the sweat accumulates.
This is more common in hot and humid weather. The infected areas may appear red, tan, or brown, with flaking, rippling, peeling, or cracking skin. It is associated with itching or a burning sensation.
Treatment is with antifungal creams containing tolnaftate, clotrimazole or miconazole applied on the affected areas, twice a day for 2 weeks.
You can also apply a glucocorticoid and anti-fungal combined medication to help reduce irritation and itching.
To cure the infection naturally, keep moist and warm areas of the body clean and dry. Powders with menthol or zinc oxide may be used, like Gold Bond medicated powder, to soothe the itch.
ref:http://en.wikipedia.org/wiki/Tinea_cruris
I have the same problem and it was real bad when i was pregnant with my son who is 3 now. This is what i do dont where underwire bras i wear sportbras and i keep it dry and when it is red i use baby powder to get rid of it.Sometimes i use A & D ointment that really works. But if it lasts to long it could be a fungus my doctor said but mine usually goes away pretty fast.I also have it under my stomach to