Pityriasis Rosea

Patient Education

What is pityriasis rosea?

Pityriasis rosea 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 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.) to10 cm (3.9 in.). The larger patches are more common. 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. The rash usually lasts 6 to 8 weeks, but it can last up to several months. The rash may take other forms. Rounded bumps (papular rash) may be seen in young children. Blisters (vesicular rash) may be seen in infants and young children. In some people, the herald patch may not appear, or two herald patches may appear close together. The pityriasis rosea rash is similar to the rash seen in other skin conditions, including ringworm of the skin, tinea versicolor, eczema, and psoriasis. A rash similar to pityriasis rosea also can be caused by syphilis and by certain medicines such as antibiotics.

How is pityriasis rosea diagnosed?

The doctor will diagnose pityriasis rosea by looking at the rash. Diagnosis can be hard when only the herald patch is visible because the condition is often mistaken for ringworm or eczema at this time. After the rash appears, diagnosis is generally clear.

If the diagnosis is unclear, we may do a potassium hydroxide (KOH) test 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).

How is it treated?

Pityriasis rosea goes away without treatment. It usually lasts about 6 to 8 weeks. If the rash itches, you may wish to use skin lotions and lubricants to soothe itching. If symptoms are severe, your doctor may prescribe anti-inflammatory medicines such as corticosteroids to relieve itching and reduce the rash.

Although treatment isn't needed, antiviral medicines like acyclovir may shorten the time you have the rash, especially if you take them when the rash first starts.

Exposing the rash to sunlight may make it go away more quickly. But exposing your skin to the sun too long can result in sunburn and increase your risk of skin cancer. Keep the itchy area cool and moist. Apply washcloths soaked in ice water. But remember that repeated wetting and drying will actually dry out your skin. Dry skin can make itching caused by a rash worse.

• Avoid taking hot showers or baths. Keep the water as cool as you can tolerate.
• Try an oatmeal bath, such as Aveeno Colloidal Oatmeal bath, to help relieve itching.