Pityriasis versicolor: symptoms, treatment and how long it lasts

The NHS says a GP or pharmacist can prescribe treatment or tell you which antifungal medicines to buy. The main treatments are an antifungal shampoo, such as ketoconazole, that you use on the affected skin and rinse off after 10 to 15 minutes, and antifungal cream. If the rash covers a large area, or shampoos and creams do not work, a GP may prescribe antifungal tablets.

The British Association of Dermatologists lists terbinafine, clotrimazole and miconazole creams, and ketoconazole and selenium sulphide shampoos used as body washes left on the skin for up to 15 minutes. Tablets such as itraconazole and fluconazole are effective but can have side effects, so they are usually reserved for widespread rashes or when topical treatment has failed.

The NHS says it causes patches of skin to change colour. On white skin the patches are usually pink, red or pale brown, and you may notice that they do not tan in the sun. On brown or black skin the patches tend to be paler than the surrounding skin.

The patches usually appear on the chest, upper back, upper arms, neck or tummy. They are flat and round, can join up to form large areas, may feel scaly and can sometimes be itchy. The British Association of Dermatologists says the rash can be mildly itchy but usually causes no trouble apart from its appearance, and often goes unnoticed if there are only a few patches.

The British Association of Dermatologists adds that sunlight causes the yeast to make chemicals that prevent tanning, so the rash stays paler than surrounding skin and is often noticed for the first time after a sunny holiday.

The British Association of Dermatologists describes it as a common and harmless rash due to an overgrowth of yeasts that live on everyone's skin. These yeasts, called Malassezia, are not related to yeast in food or to the yeasts that cause thrush. Pityriasis means fine scaling and versicolor means changing colour.

The NHS says pityriasis versicolor is different to pityriasis rosea, another skin condition with a similar-sounding name.

The NHS says it is caused by a type of fungus that lives on the skin. Most people have this fungus on their skin without any problem, but sometimes it grows and spreads more than usual. It is not always clear why.

The British Association of Dermatologists says it happens most often in warm moist climates, is most common in people in their early twenties, and that most people with it are in good health. People who get it may also have dandruff, which is caused by a similar yeast overgrowth on the scalp. It says it is not hereditary and that there is no evidence it is related to yeast in food, so there is no need to change your diet.

No. The NHS says pityriasis versicolor cannot spread from person to person. It also says it is not caused by not washing your skin, and that most people who have it are otherwise healthy.

The rash clears with treatment, but the British Association of Dermatologists says the pale areas will take several months to return to their normal colour, and that this does not mean treatment has failed. The NHS gives a similar picture: it can take a few months for the skin to return to its usual colour, and the patches can come back.

Because the yeast lives on normal skin and cannot be eradicated completely, the rash often recurs. If patches come back, you may need the same treatment again, or your GP may suggest long-term treatment, such as using antifungal shampoo every few weeks. The British Association of Dermatologists suggests washing your upper body with an anti-dandruff shampoo for a few weeks before a sunny holiday or going to a humid area.

The British Association of Dermatologists says diagnosis is usually made by a doctor looking at the rash. A special ultraviolet lamp (Wood's lamp) may be used to look for yellow fluorescence, and sometimes skin scrapings are taken. Very occasionally a skin biopsy is considered if there is doubt.

The NHS says other conditions can look similar: discoloured patches could be vitiligo, and flaky raised patches could be psoriasis. It advises not trying to diagnose it yourself and seeing a GP or pharmacist if you are worried.

The NHS says to see a GP if patches of your skin have changed colour, because if it is pityriasis versicolor it will usually only go away if treated, or if you have any other changes to your skin you are worried about. A pharmacist can also advise on treatment.

The sources used here do not describe different advice for children or pregnancy. The British Association of Dermatologists says the condition is most common in people in their early twenties. Because some antifungal medicines are not suitable in pregnancy or for young children, check with a pharmacist, GP or midwife before using a treatment.

On the NHS, pharmacists and GPs can diagnose and treat pityriasis versicolor, and the treatments are low cost and widely available. Referral to a dermatologist is rarely needed unless the diagnosis is uncertain or it keeps recurring.

Private dermatology clinics can also confirm the diagnosis with a lamp or skin scraping. Because treatment is simple and it often recurs, the useful questions are how to prevent recurrence and whether a repeat prescription or maintenance shampoo is appropriate.