Pityriasis rosea is a mild disease that causes the formation of many small patches of scaly, rose-colored, inflamed skin.
The cause of pityriasis rosea is not certain but a viral infection may be involved. However, the disorder is not thought to be contagious. It can develop at any age but is most common among young adults. Pityriasis rosea affects women more often and usually appears during spring and autumn.
Pityriasis rosea causes a rose-red or light-tan patch of skin about 1 to 4 inches (2 to 10 centimeters) in diameter that doctors call a herald or mother patch. This round or oval area usually develops on the torso. Sometimes the patch appears without any previous symptoms, but some people have a vague feeling of illness, loss of appetite, fever, and joint pain a few days before the patch appears. In 7 to 14 days, many similar but smaller patches appear on other parts of the body. These secondary patches are most common on the torso, especially along and radiating from the spine. Most people with pityriasis rosea have some itching, and in some people the itching can be severe.
Diagnosis and Treatment
A doctor usually makes the diagnosis based on the appearance of the rash, particularly the herald patch. Usually the rash goes away in 4 to 5 weeks without treatment, although sometimes it lasts for 2 months or more. Both artificial and natural sunlight may speed clearing and relieve the itching. Other standard treatments for itching may be used as needed (see Itching and Noninfectious Rashes: Treatment). Corticosteroids taken by mouth are necessary only for very severe itching.
Last full review/revision December 2006 by Peter C. Schalock, MD