What is pityriasis rosea?

Pityriasis rosea (say "pit-uh-RY-uh-sus ROH-zee-uh") is a common skin rash. It usually starts as one scaly and pinkish, purple, or red-brown patch on your stomach or back. Days or weeks later, more small patches appear. The rash may itch, but it will not spread to other people.

Experts aren't sure what causes pityriasis rosea. It may be caused by a virus.

Pityriasis rosea is most common in children and young adults. It lasts 1 to 3 months and then goes away on its own. Medicine can help relieve any itching.

Pityriasis rosea causes a rash.

• The rash often begins with a single, large, round or oval patch that is scaly with a raised border (herald patch). The patch is pink or salmon-colored on lighter skin. It is purple or red-brown on darker skin.
• Days to weeks later, smaller oval patches appear in batches on the abdomen, chest, back, arms, and legs. Patches sometimes spread to the neck or the face.
• In children, the rash often appears on the groin, armpit, scalp, or face.
• Itching is common with this rash.
• The rash usually lasts 6 to 8 weeks, but it can last up to several months.
• After the rash, your skin may look darker. This is more common in people with darker skin. The change in color goes away with time.

Before the herald patch appears, you may feel tired and like you have a cold. You may have a headache, fever, or sore throat.

Your doctor may be able to diagnose pityriasis rosea by looking at the rash. If the diagnosis is unclear, your doctor may do a potassium hydroxide (KOH) test. This test checks to make sure the rash is not caused by a fungal infection. A skin sample may be taken from the infected area and examined under the microscope (biopsy).

In a sexually active person, a test for syphilis is often done.

• If your doctor prescribed medicine, use it exactly as prescribed. Call your doctor if you have any problems with your medicine.
• Use a mild soap or a gentle skin cleanser when you wash your skin.
• Add a handful of oatmeal (ground to a powder) to your bath. Or you can try an oatmeal bath product, such as Aveeno. Keep the water warm or lukewarm. A hot bath or shower may make the rash more visible and itchy.
• Try an over-the-counter 1% hydrocortisone cream for small itchy areas. Use the cream very sparingly on the face or genitals. Note: Do not use the cream on children younger than age 2 unless your doctor tells you to. Do not use in the rectal or vaginal area in children younger than age 12 unless your doctor tells you to.

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.