Acne mechanica describes local irritation due to the skin being pressured,
occluded, rubbed, squeezed, stretched, or heated. Examples of various physi
cal traumas that provoke lesions in acne patients are given. Users of ortho
pedic crutches are at particular risk for such conditions. A crutch is anot
her extrinsic factor to be added to the list of causes of acne mechanica.