Most acne patients (99 per cent) have lesions on the face; smaller percentages exhibit acne on the back and on the chest. If subjects with physiological acne at a particular site are excluded, the percentages for each site are lower. Occasionally, in 1 per cent, severe acne is present on the back or chest alone with minimal or  no acne on  the  face.  These  observations  are in broad accordance with those made by Gotz et al. (The scalp contains  many sebaceous glands but is  probably protected from developing acne by the hairs, which prevent functional obstruction of the pilosebaceous units.)

There  is also considerable variation in the distribution of the acne at any particular site. Some areas at the same site  may be more prone to  acne than others. The infra-orbital area is usually spared, even in the severest of acne.

  Perioral acne  is  particularly evident in the early twenties. Acne  on  the back is more obvious on the upper area and is more severe laterally than medially. On the chest the acne  tends to favour the region of the shoulders and the central area. Usually,  the more severe the patient's facial acne, the more severe is the acne on the back and chest. When the acne  is severe on the back it tends to spread over towards the  sacral areas   and, if severe on the chest, then the  upper parts of the breasts may be affected.  In such situations the arms are often involved . Uncommonly the lesions may be localized to one or two areas within a particular anatomical site, such as the nose , or the middle of the cheek.