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Pityriasis Rosea
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Pityriasis Rosea - Topic Overview

What is pityriasis rosea?

Pityriasis rosea (say "pih-tih-RY-uh-sus ROH-zee-uh") is a common skin problem that causes a rash. Although it can occur at any age, it is seen most often in those between the ages of 10 and 35.

Pityriasis rosea is usually harmless. But it can cause serious problems in pregnant women.

See a picture of pityriasis rosea.

What causes pityriasis rosea?

Experts aren't sure what causes pityriasis rosea. Unlike many other skin conditions, it is not an allergic reaction or caused by a fungus or bacteria. And there aren't signs that it is caused by a virus. But something irritates the skin and causes the rash.

What are the symptoms?

Pityriasis rosea causes a rash.

  • The rash often begins with a single, round or oval, pink patch that is scaly with a raised border (herald patch). The size of the patch ranges from 2 cm (0.8 in.) to 10 cm (3.9 in.). The larger patches are more common. See a picture of a herald patch.
  • Days to weeks later, salmon-colored, 1 cm (0.4 in.) to 2 cm (0.8 in.) oval patches appear in batches on the abdomen, chest, back, arms, and legs. Patches sometimes spread to the neck but rarely to the face.
  • Patches on the back are often vertical and angled to form a "Christmas tree" or "fir tree" appearance.
  • The rash does not cause itching in 25% of people who have pityriasis rosea. For 50% of people, the itch is mild to moderate. And for 25% of people, the itch is severe.1
  • The rash usually lasts 6 to 8 weeks, but it can last up to several months.

WebMD Medical Reference from Healthwise

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