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Skin Problems

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 rare, serious problems in pregnant women, such as miscarriage or premature delivery.

See a picture of pityriasis rosea camera.gif.

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. It may be caused by a virus.

The rash does not appear to spread from person to person.

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 camera.gif.
  • 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.
  • Mild itching is a problem for about half of the people who get the rash.
  • The rash usually lasts 6 to 8 weeks, but it can last up to several months.

WebMD Medical Reference from Healthwise