Inner thigh friction as a cause of acne mechanica.

Acne mechanica is defined as being any acneiform eruption in areas of friction, pressure, stretching, rubbing, pinching, or occlusion of the skin in any individual, regardless of preexisting acne. Various causes have been reported, including prolonged back rest against a chair or bed, occlusive clothing, pressure from a prosthetic limb, and others. This is the first reported case of bilateral open comedones caused by inner thigh friction.