Pityriasis rosea (pronounced pĭt'ĭ-rī'ə-sĭs rō-zē-ə) is a rash that occurs most commonly in people between the ages of 10 and 35 but may occur at any age.
The rash (also known as Pityriasis rosea Gibert) can last several weeks to several months. Usually, there are no permanent marks as a result of this condition. However, some darker-skinned persons may develop long-lasting flat brown spots that eventually fade. Pityriasis rosea may occur at any time of year.
Pityriasis rosea begins with a large scaly pink patch on the chest or back which is called a herald or mother patch. It is often confused with ringworm but antifungal creams do not help because it is not a fungus.
Within a week or two, more pink patches appear on the chest, back, arms and legs. Patches may also occur on the neck, but rarely on the face. The patches are oval and may form a pattern over the back that resembles the outline of a Christmas tree. Sometimes the disease can produce a very severe and widespread skin eruption.
About half the patients will have some itching, especially when they become warm. Physical activities like jogging and running or bathing in hot water may cause the rash to temporarily worsen or become more obvious. There may be other symptoms including fatigue and aching. The rash usually fades and disappears within six to eight weeks, but can sometimes last much longer
The cause is unknown. Pityriasis rosea is not a sign of any internal disease, nor is it caused by a fungus, a bacterium, or an allergy. There is recent evidence suggesting that it may be caused by a virus since the rash resembles certain viral illnesses and occasionally a person feels slightly ill for a short while just before the rash appears. Pityriasis rosea does not seem to spread from person to person and it usually occurs only once in a lifetime.
The diagnosis is made by a dermatologist. Pityriasis rosea affects the back, neck, chest, abdomen, upper arms, and legs, but the rash may differ from person to person making the diagnosis more difficult.