Pityriasis versicolor

What is pityriasis versicolor?

Small numbers of the malassezia germs that causes pityriasis versicolor commonly live on the skin and do no harm. However, some people are prone to this germ multiplying and spreading on their skin more than usual, which then leads to a rash developing. Often the germ multiplies and causes the rash for no apparent reason. In some cases, hot, sunny or humid weather seems to trigger the germ to multiply on the skin. In people who sweat more it may be more likely to occur.

Pityriasis versicolor is a common fungal condition. It is more common in young adults - people in their teens and 20s. It is sometimes called tinea versicolor.

The rash

Pityriasis versicolor close-up

© Richardkiwi at nl.wikipedia (Own work), Public domain, via Wikimedia Commons

This usually starts as small pale patches. Sometimes the rash is darker than the skin in fair-skinned people, and in this case it looks like brown marks. In those with darker skin, it will be lighter than the usual colour of the skin. At first these usually appear on your back, chest, neck or upper arms.

The rash sometimes spreads to your tummy (abdomen) and thighs. Occasionally it may affect your face. More patches may appear and patches next to each other may join together. The affected skin may become slightly scaly.

Pityriasis versicolor on the forehead

© Grook Da Oger (Own work) CC BY-SA 3.0, via Wikimedia Commons

The rash is usually pale and is barely noticeable if you are fair-skinned. You may not notice it until after you sunbathe. Affected areas do not tan and therefore the rash becomes more obvious on tanned skin. The pale patches are more obvious if you have dark skin.

There are usually no other symptoms. Sometimes it is slightly itchy.

No. If you wanted an even suntan then this rash is a nuisance, as pale patches on tanned skin may look unsightly. It does not lead to any other skin conditions, or cause damage to the surrounding skin.

No - it is not possible to catch this condition from another person. The type of yeast that causes the rash is commonly found on the skin and usually does no harm. For reasons that are not clear, it seems that the germ grows out of control more easily with certain people, and causes a rash.

The type of treatment varies between cases and may depend on the location of the rash and also if you have had this condition before. It may take weeks or months for the rash to fully go after you treat it. The following are treatment options:

Ketoconazole shampoo (Nizoral®)

Ketoconazole shampoo (Nizoral®): is commonly advised. You can buy this at pharmacies and it is also available on prescription. Ketoconazole kills the germ that causes this rash. Apply the shampoo directly to affected areas and then wash off after three to five minutes. Repeat every day for five days.

Selenium sulfide shampoo

This is an alternative treatment. It is not strictly licensed for the treatment of this rash; however, it works. You can buy it from pharmacies or it is also available on prescription. Apply the shampoo to the affected areas and leave to dry for ten minutes and then rinse off. This should be repeated daily for a week. Diluting it (half water and half shampoo) may prevent it irritating your skin. This should not be used if you are pregnant. Selenium sulfide shampoo has been unavailable in the UK for some years.

Antifungal creams

These may be used if only a very small area of skin is affected. Clotrimazole (Canesten®) cream is one example. It should be applied twice a day for two or three weeks.

Antifungal tablets

Antifungal tablets may very occasionally be prescribed if the rash is over a large area of your skin, or is not cleared by the above treatments. The ones used are usually itraconazole or fluconazole.

Antifungal treatment may need to be repeated if this rash comes back (recurs) and becomes scaly again.

If you are prone to develop recurrent episodes in the sun then it may be advisable to use ketoconazole shampoo once a day for three days prior to going on holiday to the sun. This will help to prevent recurrence when you are away.

Note: after treatment, skin colour usually takes 2-3 months to return to normal. It sometimes takes even longer. As long as the rash is not scaly, this does not mean the treatment has not worked.

Some people seem prone to this yeast-like germ multiplying on their skin and the rash may come back (recur) after treatment. One option is to apply one of the above shampoos to your skin every 2-4 weeks. This may keep the germ away, or prevent the numbers building up, which will prevent the rash from recurring. Alternatively, if you have frequent recurrences then you may be advised to take antifungal tablets for one day each month as a preventative measure.