Abstract

The cause of acne is still unknown, but three factors are important in its production: excessive secretion of sebum (seborrhoea), obstruction of sebum outflow, and inflammation. Treatment aims to reduce or prevent these abnormalities, but its effects are difficult to assess, because large spontaneous variations in the severity of acne are the rule and because placebo treatment is particularly successful in acne.¹ This explains why so many different treatments are claimed to be effective.