This is a common skin disease caused by an overgrowth of the yeast fungus called Pityrosporum orbiculare (Malassezia furfur).

Most adults have Pityrosporum orbiculare on their skin; however, in a few people its presence results in a harmless skin disease.

Pityrosporum orbiculare also plays a role in the development of cradle cap (seborrhoeic dermatitis).

Pityriasis versicolor is commonly seen on the upper part of the back and on the chest, but it can be found on the entire body. In the summer the infection is seen as well-defined, uneven patches. The patches are pale-red or brownish, and scaly. The patches often merge into big blotches that may look like maps. Sunbathing evens out the colour and makes the condition less visible.

In the autumn the patches become scaly and change colour. In people who have tanned skin, this stage is quite visible as these patches appear white. It is at this point that most people first consult their doctor.

• People who suffer from profuse sweating or high production of sebum, for instance teenagers.
• People with an immunodeficiency.
• The condition is not contagious.