Pityriasis rosea

Pityriasis (pit-ih-RIE-uh-sis) rosea is a skin rash that usually begins as one large circular or oval spot on your chest, abdomen or back. Called a herald patch, this initial spot can be up to 4 inches (10 centimeters) across.

The herald patch is typically followed by a distinctive pattern of similar but smaller lesions that sweep out from the middle of your body in a shape that resembles drooping pine-tree branches.

Pityriasis rosea can affect any age group, but it most commonly occurs between the ages of 10 and 35. It usually goes away on its own within six weeks. Pityriasis rosea can cause itching, and treatment usually focuses on relieving symptoms.

Symptoms Causes Complications

Pityriasis rosea typically begins with a large, slightly raised, scaly patch — called the herald patch — on your back, chest or abdomen. Before the herald patch appears, some people experience a sore throat or fever.

A few days to a few weeks after the herald patch appears, you may notice smaller scaly spots across your back, chest or abdomen that resemble a pine-tree pattern. The rash can cause itching, which is occasionally severe.

When to see a doctor

See your doctor if you develop a persistent rash.

The exact cause of pityriasis rosea is unclear, although there is some evidence that the rash may be triggered by a viral infection, particularly by certain strains of the herpes virus. Pityriasis rosea, however, isn't believed to be contagious.

Complications of pityriasis rosea aren't likely, but if they do occur, they may include:

  • Severe itching
  • Lasting brown spots after the rash has healed, on dark skin
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