Pityriasis Rosea

Pityriasis rosea is a common rash that is usually mild and lasts about 6 to 8 weeks. Its name means that the rash has a fine-scale (pityriasis), and it tends to be pink (Rosea).

The cause of pityriasis rosea is still not known. It has been associated with some viruses in the herpes family, the same family as the cold sore virus. It can occur in clusters (in schools, families, etc.) and is more frequent in the winter. However, the risk of passing it on to anyone else is very low. It is most common between the ages of 10 and 35 years.

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People with pityriasis rosea usually feel fine, though they may be slightly unwell just before the rash starts, with a mild headache and fever, and the rash can be itchy or uncomfortable.

The first sign of pityriasis rosea is usually a single scaly pink patch, known as a ‘herald patch’ because it comes up a few days or weeks before the rash spreads. The herald patch is usually a single round or oval patch on the body and occurs in many but not necessarily all patients. It is generally larger than patches that come up later and can be confused with a patch of ringworm (tinea). A week or two later, a more widespread scaly patchy rash usually appears on the body in a pattern resembling the branches of a Christmas tree. These patches appear in crops, then slowly fade over the next 6-8 weeks. It is unusual for the rash to affect the hands, feet, or face. In people with dark skin, the patches may leave areas of darker or lighter pigmentation that may last for several months or longer. It does not leave scars.

There is no diagnostic test for pityriasis rosea, but the story of a herald patch followed by a more widespread scaly rash is usually enough for your doctor to make the diagnosis. If there is any doubt, or the rash lasts longer than two months, your doctor may recommend a skin biopsy (skin sample taken after local anesthesia) for laboratory analysis or blood tests to rule out other rashes that can look like pityriasis rosea. The herald patch can resemble ringworm, which can be ruled out if needed by sending a skin scraping sample for fungal laboratory tests.

Most people do not need any treatment. If your skin is itchy or sore, a moisturizer may help. Avoid washing the affected area with soap or shower gels as this can cause more dryness – use a soap substitute instead. Antihistamine tablets may also help and can be bought without a prescription. If the rash is still uncomfortable, a mild steroid cream or ointment such as hydrocortisone ointment can be applied twice a day. If the itch is still severe despite these treatments, your doctor may suggest a stronger steroid cream or ointment or treatment with ultraviolet light. There is some limited evidence that early antiviral treatment such as acyclovir and antibiotics such as erythromycin may speed up clearance of the rash, but it is rarely required.

• There is no need to treat the rash if it is not causing any symptoms. 
• If the rash does not clear up after three months, then a biopsy may be needed.
• There is no reason to keep children with pityriasis rosea away from school.