Pityriasis rosea

A harmless rash that starts with one large patch and then erupts. Alarming, self-limiting, and worth telling a midwife about in pregnancy.

What it is

A common, harmless, self-limiting rash, most often in older children and young adults, probably triggered by a virus.

It has a distinctive sequence. A single oval scaly patch appears first, the herald patch, usually on the trunk, often mistaken for ringworm. Days to weeks later a widespread eruption of smaller oval patches follows, arranged along the skin lines so that on the back they form a pattern often described as a Christmas tree.

It clears by itself, typically over six to twelve weeks, sometimes longer, and rarely recurs.

There is no treatment that speeds it, and none is needed. Emollients and, for itch, a mild steroid or antihistamine are all that is usually required.

Two things are worth knowing.

**In pregnancy**, particularly in the first 15 weeks, some studies have found an association with miscarriage and other complications, so it is worth telling a midwife rather than ignoring it.

And it can look like **secondary syphilis**, which classically involves the palms and soles. A rash resembling pityriasis rosea that affects the palms and soles, or occurs with other symptoms, should prompt a syphilis test, particularly given rising rates in the UK. See sexually transmitted infections.

Some medicines can cause a similar eruption.

Signs you might notice

A single oval, scaly, salmon-pink or darker patch, 2 to 10 centimetres across, often on the trunk.

Days to weeks later, many smaller oval patches on the trunk, upper arms and thighs, following the skin lines.

A fine collarette of scale at the edge of each patch.

Mild itch in most people, occasionally severe.

Sometimes a mild flu-like illness beforehand.

On brown and black skin the patches may be grey, dark brown or violet, and pigment change afterwards is common and can last months.

See a GP: to confirm the diagnosis; if the rash involves palms and soles, which needs a syphilis test; if pregnant; if the itch is severe; or if it has not cleared in three months.

Urgent: fever, feeling unwell, blistering, mouth or eye involvement, or a rash after starting a new medicine, which may be a serious drug reaction. See Stevens-Johnson syndrome.

How it can affect day-to-day life

The main need is reassurance with a timeframe. A widespread rash appearing over days is frightening, and being told it is harmless and will take two to three months to go, rather than a week, prevents repeated appointments and unnecessary treatment.

It is not contagious in any practical sense, and there is no need to stay off school or work.

Hot baths and showers worsen the itch; lukewarm water and emollients help.

Sunlight may help slightly, though not enough to justify deliberate exposure.

On darker skin the pigment changes afterwards can be more distressing than the rash itself, and take months to settle; that should be mentioned in advance.

The herald patch is very frequently treated as ringworm with antifungal cream for weeks before the rest appears, at which point the diagnosis becomes obvious.

Recurrence is uncommon, which is genuinely reassuring for people who ask.

Supporting someone well

Get the diagnosis confirmed rather than treating a herald patch as ringworm indefinitely.

Expect six to twelve weeks; say so, because that is the main source of anxiety.

Use emollients, lukewarm rather than hot water, and a mild steroid or antihistamine for itch.

Tell a midwife if pregnant.

Ask for a syphilis test if the palms and soles are involved.

Do not stay off school or work; it is not meaningfully contagious.

Expect pigment changes afterwards on darker skin, lasting months.

Get any rash with fever, blistering or mouth involvement assessed urgently.

Review any new medicine started before the rash.

Where to get help

A GP practice for diagnosis and reassurance.

A sexual health clinic for syphilis testing if the palms and soles are involved.

A pharmacist for emollients and antihistamines.

British Association of Dermatologists publish a patient leaflet on pityriasis rosea.