What Is It?
Pityriasis rosea is a harmless skin disease that causes scaly patches that sometimes itch over the torso, neck, arms and legs. Anyone can get it, but it is most common in people ages 10 to 35.
Typically, the disease begins with the appearance of a single large, pink, scaly, oval patch, called the "herald patch." This patch is approximately 1 inch to 2 inches long. It tends to have a salmon-colored center surrounded by a darker pink ring, which some patients mistake as a sign of ringworm.
Within about two weeks, many smaller patches appear, sometimes hundreds of them. They are mildly itchy and appear mainly on the abdomen and back. On the back, the patches tend to line up along the ribs, giving the rash a distinct "Christmas tree" pattern. The rash goes away on its own, usually within two months. Any skin discoloration from the rash will fade after another few months.
No one knows what causes pityriasis rosea. It seems to occur most often in spring and autumn. It is not contagious, and it does not lead to any other disorder.
The main symptoms of pityriasis rosea are the appearance of the herald patch followed by a more diffuse rash of smaller patches. The patches tend to be oval, scaly, and dry to the touch. They may be pink, red or brown and generally appear on the abdomen, back, neck, arms and legs. Only rarely do the patches appear on the face.
Sometimes, the rash can be associated with mild itching.
In most cases, a physician or dermatologist can diagnose pityriasis rosea simply by looking at it. Although there is no specific blood test to diagnose pityriasis, blood testing may be ordered to exclude other diagnoses. If there is any question of a skin fungus, a scraping of the edge of a spot will be placed on a slide and examined under the microscope. Rarely, a skin biopsy is needed to confirm the diagnosis. In a biopsy, a small piece of tissue is removed and sent to a laboratory to be examined.
After the initial rash, or herald patch, appears, the secondary rash of smaller patches appears within about two to 14 days. This more widespread rash generally lasts three to eight weeks but may linger for months.
Because no one knows what causes pityriasis rosea, there is no way to prevent it. It does not appear to be contagious.
There are no treatments that cure pityriasis rosea; the disease must run its course. However, the itching can be treated in several ways. For mild itching, an over-the-counter anti-itch ointment (such as calamine lotion) or corticosteroid cream (such as Cortizone-10 or Cortaid) may be enough to provide relief. For more severe itching, stronger steroid creams may be prescribed. For itching that occurs mainly at night, oral antihistamines may reduce itching and make you drowsy enough to fall asleep more easily.
In very severe cases in which the rash lasts longer than usual, or if the rash covers a large part of the body, ultraviolet (UV) light therapy may be recommended. Doses of UV-B rays, similar to the sun's rays, are given by exposing the skin to the light rays for short periods of time over several days. The skin may turn slightly red, similar to a mild sunburn.
The red spots may appear more prominently after a hot shower or bath and after heavy physical activity. The condition doesn't get worse, the rash simply becomes more noticeable.
When To Call A Professional
See a health care professional if you or your child develops an unexplained rash. Although specific treatment is not necessary for pityriasis rosea, its symptoms mimic other skin diseases, such as ringworm, that should be treated. Your physician can diagnose the problem and recommend appropriate treatment.
The prognosis is excellent. Most cases clear up in two months. The rash rarely returns. Although some people, especially those with dark skin, experience some skin discoloration from the rash spots, it usually fades with time. Generally, there are no residual effects.
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