Pityriasis rosea (Pit-ih-RYE-ah-sis Ro-ZEA) is a rash that can occur at any age but it occurs most commonly in people between the ages of 10 and 35 years. The rash can last from several weeks to several months. Usually there are no permanent marks as a result of this disease, although some darker-skinned persons may develop long-lasting flat brown spots that eventually fade.
The condition often begins as a large, single pink patch on the chest or back. This patch may be scaly and is called a "herald" or "mother" patch. Often the person with this condition will think this patch is ringworm and will apply creams that are used to treat fungus. This will not help since a fungus does not cause the rash.
Within a week or two, more pink patches (sometimes hundreds of them!) appear on the body and on the arms and legs. Patches may also occur on the neck, and though rare, the face. These spots usually are smaller than the "herald" patch and may also be mistaken for ringworm. The patches are oval and often form a pattern over the back that resembles the outline of a Christmas tree. Sometimes the disease can produce a more severe and widespread skin eruption. About half the patients will have some itching, especially when they become over-heated.
Occasionally there may be other symptoms, including tiredness and aching. The rash usually fades and disappears within six to eight weeks, but can sometimes last much longer. Physical activity—like jogging and running, or bathing in hot water—may cause the rash to temporarily worsen or reappear. In some cases, the patches will reappear up to several weeks after the first episode and can continue for many months.
The cause is unknown. It is not caused by a fungus or bacteria. It also is not due to any type of allergy. Pityriasis rosea is not a sign of any internal disease.
A virus may cause a rash. Like other known viral diseases, pityriasis rosea usually occurs only once in an individual, and occasionally makes those affected feel slightly ill. But the virus theory has not been proven. Unlike many viruses, however, pityriasis rosea does not seem to spread from person to person.
Diagnosis is usually made by a dermatologist, a physician with special training in skin diseases. Pityriasis rosea usually affects the back, neck, chest, abdomen, upper arms and legs. The rash may differ from person to person, making the diagnosis more difficult. The numbers and sizes of the spots can also vary and occasionally the rash can be found in an unusual location, such as the lower body or on the face. Fungus infections, like ringworm, may resemble this rash. Reactions to certain medications, such as antibiotics, "water pills" and heart medications can also look the same as pityriasis rosea.
The dermatologist may order blood tests, scrape the skin or take a sample from one of the spots (skin biopsy) and examine it under a microscope to make the diagnosis.
Treatment may include external or internal medications for itching. Soothing medicated lotions and lubricants may be prescribed. Lukewarm rather than hot baths may be suggested. Strenuous activity that could aggravate the rash should be avoided. Ultraviolet light treatments given under the supervision of a dermatologist may be helpful.
Occasionally anti-inflammatory medications such as corticosteriods may be necessary to stop itching or make the rash go away. Patients should be reassured that this disease is not a dangerous skin condition even if it occurs during pregnancy.
Remember that pityriasis rosea is a common skin disorder and is usually mild. Most cases usually do not need treatment and fortunately even the most severe cases eventually go away.