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Pityriasis rosea

Definition

Pityriasis rosea is a common type of skin rash seen in young adults.

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Causes, incidence, and risk factors

Pityriasis rosea is believed to be caused by a virus. It occurs most often in the fall and spring.

Although pityriasis rosea may occur in more than one person in a household at a time, it is not thought to spread from one person to another.

Symptoms

Attacks most often last 4 - 8 weeks. Symptoms may disappear by 3 weeks or last as long as 12 weeks.

The rash starts with a single large patch called a herald patch. After several days, more skin rashes will appear on the chest, back, arms, and legs.

The skin rashes:

Are often pink or pale red
Are oval in shape
May be scaly
May follow lines in the skin or appear in a "Christmas tree" pattern
May itch

Signs and tests

Your health care provider can usually diagnose pityriasis rosea by the way the rash looks.

Rarely, the following tests are needed:

A blood test to be sure it is not a form of syphilis, which can cause a similar rash
A skin biopsy to confirm the diagnosis

Treatment

If symptoms are mild, you may not need treatment.

Gentle bathing, mild lubricants or creams, or mild hydrocortisone creams may be used to soothe irritation.

Antihistamines taken by mouth may be used to reduce itching. You can buy antihistamines at the store without a prescription.

Moderate sun exposure or ultraviolet (UV) light treatment may help make the rash go away more quickly. However, you must be careful to avoid sunburn.

Expectations (prognosis)

Pityriasis rosea usually goes away within 6 - 12 weeks. It doesn't usually come back.

Calling your health care provider

Call for an appointment with your health care provider if you have symptoms of pityriasis rosea.

References

Habif TP. Psoriasis and other papulosquamous diseases. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier;2009:chap 8.

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