This is a common skin disease caused by an overgrowth of the yeast fungus called Pityrosporum orbiculare (Malassezia furfur) on the skin surface. The growth of these organisms relies on the presence of mature sebaceous (oily) glands; therefore it is not common before puberty, and mainly affects young adults.

Most adults have these organisms on their skin and normally they do not cause any skin problems. However, during the hot and wet seasons, in subtropical and tropical regions, they may grow excessively and result in a harmless skin disease. Most sufferers first notice this problem after the summer, which then spread gradually.

Profuse perspiration and high production of sebum (oil) by the skin make it easier for the fungus to multiply and spread, for instance in teenagers, but the condition is not contagious.

Signs

Pityriasis versicolor is commonly seen on the upper part of the back, the neck, and the chest, but it can be occasionally found on the entire body.

In the beginning, there are only a few small patches, often unnoticed. The growth is very slow and may take a few months before they are noticed.In the summer the infection is seen as well-defined, uneven patches. The patches are pale-red or brownish, and often merge into big irregular blotches. The surface is slightly scaly when lightly scratched with a sharp object. The fine scales are signs of active infection, because when it is treated, they are no longer present.

The colour may be unstable and vary from a lighter to a darker hue when compared to the surrounding skin. The organisms may inhibit the formation of melanin pigment, and as a result, the patches are much whiter in colour, and will not tan after exposure to sun, whereas the surrounding will tan as usual. Therefore the contrast is increased and it may be the first time that they are noticed after the person has spent a sunny weekend on the beach. White patches will take a long time to return to normal skin colour even after successful treatment.

In some people, Pityrosporum orbiculare infects the hair follicles on the back and on the chest, which causes highly itchy acne-like spots to appear.This condition is called pityrosporum folliculitis, and it is more common in people who are between 30 and 40 years of age, particularly women.

Diagnosis

Skin scrapings, when treated with special dyes, will show the yeast organisms under microscopy. The patches may show a slight fluorescent yellow when examined under ultra-violet light (Wood's light examination). However, these are usually unnecessary as the signs are quite typical to be recognised.

Treatments

It mainly relies on topical treatments. Shampoo containing selenium sulphide or ketoconazole can be used to wash the area. It is very useful for large affected area. Alternatively it can be put on directly for a few hours every day. The problem with the selenium sulphide shampoo is the unpleasant smell.

Anti-fungal preparations in creams or sprays can be used twice daily for 3 to 4 weeks. In general, oral anti-fungals, such as itraconazole, are not necessary unless in severe cases, or in pityrosporum folliculitis.

The flakiness will disappear after successful treatment, but the whitened patches will not return to normal skin colour straight away. No further treatment is needed, and it will just take a longer time.

The condition is likely to recur, which can be prevented by washing with either selenium sulphide or ketoconazole shampoo.