Condition Basics

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.

What causes it?

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, large, round or oval patch that is scaly with a raised border (herald patch). The patch is pink or salmon-coloured 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 colour 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.

How is it diagnosed?

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.

How is pityriasis rosea treated?

Pityriasis rosea usually goes away without treatment within 6 to 8 weeks. If the rash itches, there are over-the-counter medicines that can help. Or your doctor may prescribe a cream or ointment.

Severe cases of pityriasis rosea may be treated with medicines or with ultraviolet light therapy. Also, if you are pregnant and get this rash, check with your doctor since you may need treatment.

If the rash lasts more than 3 months, contact your doctor.

Home treatment

To relieve itching at home:

• Try to stay cool. Getting too warm and sweaty can make the rash and itching worse.
• Avoid taking hot showers or baths. Keep the water warm or lukewarm.
• Add a handful of oatmeal (ground to a powder) to your bath. Or you can try an oatmeal bath product, such as Aveeno.
• 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.
• Try an over-the-counter antihistamine. Don't give antihistamines to your child unless you've checked with the doctor first. Be safe with medicines. Read and follow all instructions on the label.
• Apply a moisturizer or calamine lotion to the skin while it is damp.
• Use a mild soap or a gentle skin cleanser when you wash your skin.