Pityriasis versicolor mostly affects the skin of the upper thorax; less often the proximal extremities. It is caused by a commensal lipophilic yeast, Pityrosporum ovale (Malassezia furfur). This yeast is hosted by virtually all people. Do not call this a contagious disease! The most effective therapy is ketoconazole, either as a topical shampoo or an oral single dose of 400 mg preferably with an acidic drink. A single dose of ketoconazole is not a risk as regards hepatic welfare.