Pityriasis rosea is a disease that causes the formation of many small patches of scaly, rose-colored or tan-colored, inflamed skin.
The cause of pityriasis rosea is not certain, but an infection with human herpesvirus type 6, 7, or 8 may be involved. However, the disorder is not thought to be contagious. Pityriasis rosea most commonly occurs in people between the ages of 10 and 35 years. Pityriasis rosea affects women more often.
Pityriasis rosea causes a rose-colored or tan-colored patch of skin about 1 to 4 inches (2 to 10 centimeters) in diameter that doctors call a herald or mother patch. The rose or tan color is not as obvious in people with darker skin. 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, headache, and sometimes 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. In children, the patches commonly begin in the groin or underarms and spread outward. Children and pregnant women may have little or no scaling. Most people with pityriasis rosea have some itching, and in some people the itching can be severe.
A doctor usually makes the diagnosis based on the appearance of the rash, particularly the herald patch.
Usually the rash goes away within 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 Treatment). Corticosteroids taken by mouth are necessary only for very severe itching.
Because erythromycin can help decrease inflammation, doctors may give people this drug by mouth to help the rash go away sooner and be less severe. Although erythromycin is an antibiotic, it is not used in this case to kill bacteria.
Last full review/revision December 2014 by Peter C. Schalock, MD