Is pityriasis rosea contagious?

It is not considered contagious in any meaningful sense. Despite its probable viral link, it is extremely rare for it to spread between people, even within households, and there is no need to stay off work or school or avoid contact with others. Outbreaks in families or close groups have occasionally been reported but are the exception.

How long will the rash last and will it leave scars?

Most cases clear within six to ten weeks, though a few last up to three or four months. It does not scar. In people with darker skin, the patches can leave temporary darker or lighter marks that fade over several months. Recurrence is uncommon, happening in only a small minority of people.

Is pityriasis rosea dangerous in pregnancy?

For most pregnant women it is harmless, but some studies have suggested a possible link between pityriasis rosea in early pregnancy, particularly before 15 weeks, and a higher risk of complications. The evidence is not conclusive. If you are pregnant and develop the rash, let your midwife or doctor know so they can confirm the diagnosis and monitor your pregnancy as appropriate.

DermatologicalICD-10: L42Common; mainly affects adolescents and young adults, with most people having only one episode

Pityriasis Rosea

Also known as: Herald patch rash, Christmas tree rash

Pityriasis rosea is a common, harmless skin rash that mostly affects teenagers and young adults. It usually begins with a single oval, pink, slightly scaly patch, called the herald patch, on the chest, back, or abdomen. A week or two later, many smaller oval patches appear across the trunk and upper limbs, often following the lines of the ribs in a pattern described as resembling a Christmas tree. The rash can look alarming and may itch, but it is not contagious in any practical sense, is not caused by poor hygiene, and clears by itself, usually within six to ten weeks, without leaving scars. Its cause is not fully understood but it is thought to be linked to reactivation of certain human herpesviruses, and it rarely recurs.

At a Glance

Common symptoms: A single larger oval pink or salmon-coloured patch (the herald patch), 2 to 10 cm across, with a fine scaly border, A widespread rash of smaller oval patches on the chest, back, abdomen, and upper arms and thighs appearing 1 to 2 weeks later, Patches aligned along skin creases, giving a 'Christmas tree' pattern on the back
Main treatments: No treatment is needed in most cases; the rash resolves on its own within 6 to 10 weeks, Emollients and soap substitutes to soothe dryness and itch, Mild to moderate topical corticosteroid creams for itchy patches
Category: Dermatological · Common; mainly affects adolescents and young adults, with most people having only one episode
See a doctor if: Any new widespread rash, to confirm the diagnosis and rule out ringworm, psoriasis, eczema, or syphilis

Symptoms

A single larger oval pink or salmon-coloured patch (the herald patch), 2 to 10 cm across, with a fine scaly border

A widespread rash of smaller oval patches on the chest, back, abdomen, and upper arms and thighs appearing 1 to 2 weeks later

Patches aligned along skin creases, giving a 'Christmas tree' pattern on the back

Mild to moderate itching, sometimes worse when hot or sweating

Occasionally mild tiredness, headache, or sore throat in the days before the rash

In darker skin, patches may appear grey, violet, or dark brown, and may leave temporary dark or light marks

Causes

Likely reactivation of human herpesvirus 6 or 7 (the viruses that cause roseola in infancy), though this is not proven
Not caused by bacteria, fungi, or allergies
Rarely, a similar rash can be triggered by certain medications or vaccinations
Possibly a mild immune response to the virus within the skin, which may explain the flu-like symptoms some people notice beforehand

Risk Factors

Age 10 to 35
Spring and autumn, when cases are slightly more common
Recent viral illness
Pregnancy (the rash is usually harmless but is discussed with a midwife or doctor)

Diagnosis

Clinical examination; the herald patch and the pattern of the rash are usually distinctive
A skin scraping to rule out fungal infection (ringworm) if the herald patch is the only lesion
Blood test for syphilis in some adults, because secondary syphilis can cause a similar rash
Skin biopsy only if the rash is unusual or persists beyond three months

Treatment

No treatment is needed in most cases; the rash resolves on its own within 6 to 10 weeks
Emollients and soap substitutes to soothe dryness and itch
Mild to moderate topical corticosteroid creams for itchy patches
Oral antihistamines to help with itch and sleep
Phototherapy (UVB) or a course of oral acyclovir in extensive or persistent cases, under specialist advice
Supportive: lukewarm rather than hot showers, loose cotton clothing, and avoiding sweating and strenuous exercise, which can worsen itch

Prevention

There is no known way to prevent pityriasis rosea
It is not practically contagious, so no isolation or special precautions are needed
Keep the skin well moisturised to reduce itch and irritation if the rash appears
Avoid overheating, which can intensify the rash and itching

When to See a Doctor

Any new widespread rash, to confirm the diagnosis and rule out ringworm, psoriasis, eczema, or syphilis
Severe itching that disrupts sleep or daily life
A rash lasting longer than three months
Rash during pregnancy, particularly in the first 15 weeks
Fever, feeling unwell, or a rash involving the palms, soles, or mouth, which suggests a different condition

Frequently Asked Questions

Related Conditions

Ringworm

Infectious

Psoriasis

Dermatological

Eczema

Dermatological

Syphilis

Infectious

Roseola

Pediatric

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