Pityriasis versicolor

Health and Nutrition > Diseases > P Reviewed by John Pillinger, GP

What is pityriasis versicolor?

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).

What causes it?

Everyone gets Pityrosporum orbiculare on their bodies at some point in life. This causes the person no problems unless it starts to grow excessively. Little is known of why this happens, but pityriasis versicolor is very common in subtropical and tropical regions.

It is liable to flourish during the summer in this country. Profuse perspiration and high production of sebum (oil) by the skin make it easier for the fungus to multiply and spread.

An immunodeficiency, for example HIV infection, also makes it easier for the fungus to spread.

What are the symptoms?

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.

Who is at most risk?

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

How is it diagnosed?

Many other skin diseases that require a completely different treatment can cause the same symptoms as pityriasis versicolor, so it is very important that the doctor's initial diagnosis is confirmed by tests.

A scrape should be taken for microscopy and cultivation in a laboratory.

Pityrosporum orbiculare gives out yellow-green when exposed to ultraviolet light (Wood's light examination).

What is the treatment?

The outbreaks are treated with selenium sulphide shampoo (Selsun) (unlicensed use), or ketoconazole (Nizoral) shampoo or cream. Selenium shampoo is applied to the body and rinsed off after 30 minutes every day for a week. Ketocanazole shampoo is used to wash the body for five minutes once daily for five days.

In severe cases, the doctor may choose a treatment with itraconazole capsules. This treatment should also be followed up with preventive treatments in the subsequent year.

Pityriasis versicolor can be prevented from reappearing by washing with either selenium sulphide shampoo, or ketoconazole shampoo. Talk to your doctor about this.

What can be done at home?

The condition is likely to recur, so it is recommended that the preventive treatment is started in the spring.

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