What is pityriasis rosea?
Pityriasis rosea is a skin condition that arises suddenly, is probably “triggered” by a virus infection, and disappears again spontaneously within about 2 months.
What does pityriasis rosea look like?
The condition is usually preceded by a mild cold or headache. A single patch a few centimetres across then arises — bright red, scaling at the edge — usually on the chest or back. This is called the “herald patch” (plaque mère, or mother patch). In the following days, similar patches arise over the rest of the trunk, arms and legs. The pattern of the slightly oval spots, running in the direction of the skin lines, often resembles the drooping branches of a fir tree on the back. The patches sometimes itch slightly, but usually cause few complaints. The condition disappears by itself again after a few weeks (2–8).
Who can get pityriasis rosea?
Pityriasis rosea is seen mainly in young people aged 10–35.
What causes pityriasis rosea?
There was long speculation about an infection as the cause of pityriasis rosea, with the infection (elsewhere in the body) producing the skin reaction. Various investigations into bacteria and fungi as the cause have yielded nothing. It is currently fairly generally assumed that a mildly running virus infection triggers the skin reaction. A relationship between the development of the rash and the use of medicines is not very likely.
How is it treated?
Pityriasis rosea disappears by itself. If necessary the itch can be treated with menthol gel or a mild corticosteroid cream. Light therapy (UVB) can be useful in some cases. Episodes of pityriasis rosea are usually a one-off.
When to see a doctor
See your GP or a dermatologist to confirm the diagnosis, especially if the rash is very itchy, does not begin to clear within about 8 weeks, or if you are pregnant (pityriasis rosea in pregnancy is worth discussing). Assessment also helps rule out conditions it can resemble, such as a fungal infection or a drug rash.