Pityriasis rosea is an oval-shaped rash that’s typically raised and scaley. The underlying cause isn’t clear, but experts suspect it’s related to viral infections.

Skin rashes are common and can have many causes, from an infection to an allergic reaction. If you develop a rash, you’ll likely want a diagnosis so that you can treat the condition and avoid future rashes.

Pityriasis rosea, also called a Christmas tree rash, is an oval-shaped skin patch that can appear on different parts of your body. This is a common rash that affects people of all ages, although it typically occurs between the ages of 10 and 35.

A Christmas tree rash causes a distinct raised, scaly skin patch. This skin rash differs from other types of rashes because it appears in stages.

Initially, you may develop one large “mother” or “herald” patch that can measure up to 4 centimeters. This oval or circular patch can appear on the back, abdomen, or chest. In most cases, you’ll have this single patch for a few days or weeks.

Eventually, the rash changes in appearance, and smaller round scaly patches form near the herald patch. These are called “daughter” patches.

Some people only have a herald patch and never develop daughter patches, whereas others only have smaller patches and never develop a herald patch, although the latter is rare.

The smaller patches typically spread and form a pattern resembling a pine tree on the back. Skin patches don’t usually appear on the soles of the feet, face, palms, or scalp.

A Christmas tree rash can also cause itching, which can be mild, moderate, or severe. About 50 percent of people with this skin condition experience itchiness, according to the American Academy of Dermatology (AAD).

Other symptoms that may occur with this rash include:

  • fever
  • sore throat
  • tiredness
  • headache

Some people experience these symptoms before the actual rash appears.

The exact cause of a Christmas tree rash is unknown. Although the rash can resemble hives or a skin reaction, it’s not caused by an allergy. In addition, fungus and bacteria don’t cause this rash. Researchers believe pityriasis rosea is a type of viral infection.

This rash doesn’t appear to be contagious, so you can’t catch a Christmas tree rash by touching someone’s lesions.

See your doctor if you or your child develops an unusual skin rash. Your doctor may be able to diagnose the rash upon observing your skin, or your doctor may refer you to a dermatologist, a specialist who treats conditions of the skin, nails, and hair.

Although common, pityriasis rosea isn’t always easy to diagnose because it can look like other types of skin rashes, such as eczema, psoriasis, or ringworm.

During the appointment, your doctor will examine your skin and the rash pattern. Even when your doctor suspects a Christmas tree rash, they may order blood work to eliminate other possibilities. They may also scrape off a piece of the rash and send the sample to a laboratory for testing.

Treatment isn’t necessary if you’re diagnosed with a Christmas tree rash. In most cases, the rash heals on its own within one to two months, although it can persist for up to three months or longer in some cases.

While you wait for the rash to disappear, over-the-counter treatments and home remedies can help sooth itchy skin. These include:

Speak with your doctor if itching becomes unbearable. Your doctor may prescribe a stronger anti-itch cream than what’s available at the drug store. As with psoriasis, exposure to natural sunlight and light therapy may also help calm skin irritation.

Exposure to UV light can suppress your skin’s immune system and reduce irritation, itchiness, and inflammation. If you’re thinking about light therapy to help ease itching, the Mayo Clinic warns that this type of therapy may contribute to skin discoloration once the rash heals.

Some people with darker skin develop brown spots once the rash disappears. But these spots may eventually fade.

If you’re pregnant and develop a rash, see your doctor. A Christmas tree rash in pregnancy has been linked with a greater chance of miscarriage and premature delivery. There doesn’t appear to be any way to prevent this condition. Therefore, it’s important that your doctor is aware of any developing rash so that you can be monitored for pregnancy complications.

A Christmas tree rash isn’t contagious. It rarely recurs and doesn’t cause permanent skin scarring.

But although this rash doesn’t typically cause lasting problems, see your doctor for any persistent rash, especially if it worsens or doesn’t improve with treatment.

If you’re pregnant, talk with your doctor if you develop any type of rash. Your doctor can determine the type of rash and discuss the next steps with you.