What is this rash? What's wrong with my skin? Is it serious?

These are typical questions among patients diagnosed with pityriasis rosea. Although the name may sound serious, patients are usually reassured when they hear that it is actually a common, harmless skin disease. It's not pleasant, but not serious.

In fact, the only symptom some people complain of is itching, which usually is very mild and most often noticed after getting out of the bath or shower.

Whether or not it is contagious is unknown, because its cause is unknown. There is evidence that it could be viral because small outbreaks have occurred in fraternity houses and some military bases.

Pityriasis is seen in more women than men by a 1.5-to-1 margin. Pityriasis usually occurs in people ages 10 to 35 (mean age is about 23 years old). The incidence of disease is higher during the colder months. About one-fifth of affected persons may have had a recent upper respiratory infection.

This rash appears to be seen more in persons with personal or family history of one or more of the following: hay fever, asthma, very dry skin and eczema.

The first skin spot seen (also called a lesion or plaque) is typically round or oval in shape and appears abruptly. At this stage, many people are convinced they have ring worm. The first patch (called the herald patch) is often misdiagnosed as eczema. A few days to weeks later, there may be more lesions that are smaller than the initial one. These lesions can be anywhere on the body but are not usually on the face. Very few affected patients get lesions inside the mouth.

Individual lesions are salmon in color in people with lighter skin tones and may be darker than the skin in people with darker skin tones. A fine, tissue-like scale is attached to the border of the lesion. The number of lesions can vary from a few to several hundred. If a person has numerous lesions on the back, they may give the appearance of a drooping pine tree. This is commonly known as "Christmas tree distribution."

Treatment is usually not needed for the lesion because it is benign and self-limited, meaning it disappears or resolves by itself.

Moisturizing the skin during the first two weeks of the rash can minimize itching. Ultraviolet-light therapy or sun exposure can sometimes help the healing process.

Pityriasis rosea usually resolves on its own in six to eight weeks, and the skin returns to its normal appearance. It does not leave scars. However, in some cases, it can take as long as 12 weeks to resolve. If the rash lasts longer than 12 weeks, medical evaluation should be sought.