Christmas tree rash (pityriasis rosea)

Christmas tree rash (pityriasis rosea) is a fine, itchy, scaly rash that usually appears first as a single patch on the chest, abdomen or back. After this first appearance (herald patch), the rash may spread as small patches to other parts of the back and chest and to the limbs. The rash may form a pattern on the back that resembles the outline of a Christmas tree.

Christmas tree rash usually resolves without treatment within six to eight weeks, but it can last several months. Medicated lotions may lessen itchiness and may help hasten its disappearance, but they're often not required.

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 serious problems in pregnant women.

What causes pityriasis rosea?

The cause of pityriasis rosea is unknown. Unlike many other skin conditions, it is not an allergic reaction or caused by a fungus or bacteria. Some experts think it may be caused by a virus. But neither signs of a virus (such as its genetic material) nor symptoms of a viral infection (such as a fever) are found in everyone with pityriasis rosea.

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.

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, pregnant women, and people with dark skin. 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.

Before the herald patch appears, you may feel tired and as though you have a cold. You may have a headache, nausea, sore throat, and loss of appetite.

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.

If you get a rash on the palms of your hands or the soles of your feet, see your doctor. This can be a sign of something more serious than pityriasis rosea.