Patches of skin may be darker or lighter than your normal skin colour, or may be red, brown or pink. They tend to develop gradually and may join up to form larger patches over time.
The areas most often affected by pityriasis versicolor include the back, chest, upper arms, neck and tummy.
Although it may look unpleasant and the patches are sometimes itchy, pityriasis versicolor is harmless.
You may still want to see a GP, as it usually only improves with treatment. They can normally diagnose pityriasis versicolor by examining your skin.
Why it happens
Pityriasis versicolor is caused by a type of yeast called Malassezia. This yeast is found on the skin of more than 90% of adults, where it normally lives without causing any problems.
But pityriasis versicolor can develop if this yeast starts to multiply more than usual. It's not clear exactly why this happens in some people and not in others.
Several factors can increase your risk of developing pityriasis versicolor, including:
- living or staying in a warm, moist environment, including the UK, in the summer
- sweating excessively (hyperhidrosis)
- creams, dressings or clothing that do not allow your skin to breathe
- being malnourished
- having a weakened immune system
- being a teenager or in your early 20s
Pityriasis versicolor is not related to poor hygiene. The condition cannot be spread from person to person because most people already have the Malassezia yeast on their skin.
How pityriasis versicolor is treated
Pityriasis versicolor can be treated with antifungal medicines. These are available as shampoos, creams and tablets.
Antifungal shampoos (such as ketoconazole or selenium sulphide shampoo) are often the first treatment recommended for pityriasis versicolor.
These are available to buy over the counter from pharmacies, or a GP can prescribe them.
In most cases, these shampoos need to be made into a lather and left on the affected areas of skin for 5 to 10 minutes before being rinsed off. This usually needs to be repeated every day for 5 to 7 days.
You may experience some skin dryness or irritation when using these shampoos, particularly selenium sulphide.
It may be helpful to dilute the shampoo with water before applying it. Some people also find the odour of selenium sulphide shampoo unpleasant.
If only small areas of skin are affected, a GP may prescribe an antifungal cream.
These creams usually need to be applied to the affected area of skin once or twice a day for several weeks.
Some people experience a burning sensation when they use these antifungal creams, but this is not common.
If a large area of skin is affected or other treatments have not helped, you may be prescribed antifungal tablets.
These usually need to be taken once a day for 1 to 4 weeks.
Side effects of these tablets are uncommon, although some people experience problems such as rashes, feeling sick and tummy (abdominal) pain while taking them.
Overall, antifungal shampoos, creams and tablets are effective in killing the yeast that causes pityriasis versicolor.
But it can take several weeks or months for your skin to return to its normal colour. In more persistent cases, treatment may need to be repeated.
It's common for pityriasis versicolor to come back after treatment, particularly during the summer or during holidays to warm and humid countries.
But you can reduce this likelihood by regularly using the antifungal shampoos mentioned above.
For example, using the shampoo once a day for a few days before going on holiday can help prevent pityriasis versicolor recurring.
As these shampoos are available to buy from pharmacies, you do not need to see a GP for a prescription if you run out.
If you develop pityriasis versicolor again after treatment, you can try treating it yourself with antifungal shampoo, or see a GP for advice and other treatments.
If you have frequent and severe episodes of pityriasis versicolor, a GP may consider prescribing antifungal tablets to take a few times a month to prevent the condition recurring.
They may also refer you to a skin specialist called a dermatologist.
Pityriasis versicolor or vitiligo?
Pityriasis versicolor can sometimes be confused with vitiligo, as they both cause the skin to become discoloured in patches.
But there are ways to tell the difference:
- vitiligo often develops on both sides of your body at the same time, whereas pityriasis versicolor may not
- skin affected by vitiligo usually has a normal texture, whereas areas affected by pityriasis versicolor are usually slightly scaly or flaky
- vitiligo is more common around the mouth, eyes, fingers, wrists, armpits and groin, whereas pityriasis versicolor tends to develop on the back, chest, upper arms, neck and tummy