An itchy rash that appears on inner thighs is known as intertrigo, or an inflammation of the body folds or two skin surfaces due to their friction and irritation.
It usually develops from the chafing of warm, moist skin in the areas of the inner thighs and genitalia, the armpits, under the breasts, the underside of the belly, behind the ears, and the web spaces between the toes and fingers.
Intertrigo occurs more often among overweight individuals, those with diabetes and eczema.
Try to put some baby diaper rash ointment such as a topical zinc oxide cream, clean the area with antibacterial soap and keep it dry.
Avoid to use thigh cloths and underwear.