Pityriasis rosea causes a rash that most often occurs during the spring or fall in those ages 10 to 35. It typically starts as a single round or oval patch 2 to 10 centimeters across called a herald patch. Days to weeks later, the rash sweeps across an area in the body, appearing in batches of one to two centimeter pinkish oval patches. Pityriasis rosea most commonly occurs on the abdomen, chest, back, arms and legs and usually lasts six to eight weeks but in some cases, can last months.
It is unknown what causes pityriasis rosea. Researchers think it may be related to a relapse of to the Human Herpes Virus type 7 (HH7), which is a virus we are exposed to as children and usually build up a tolerance to. Before developing the herald patch, a person developing pityriasis rosea may feel like they are coming down with a cold or have other symptoms such as a headache, nausea, sore throat or loss of appetite.
Itching occurs in 75 percent of all people with pityriasis rosea, with 25 percent complaining of severe itchiness. There usually are no scars left from the rash though darker skinned people may be left with some spots on their skin after it heals. African American children with pityriasis rosea have about 30 percent more facial and scalp involvement than Caucasian children and are more likely to be left with areas of darker pigmentation.
To diagnose pityriasis rosea, a doctor may take a skin scraping or a biopsy to rule out whether a fungus is the cause of the rash. Pityriasis rosea can also resemble a drug rash from antibiotics and the herald patch can be mistaken for eczema or ringworm.
In most cases, no treatment is needed for pityriasis rosea; it resolves on its own. In more severe cases oral steroids may be used. Oral antihistamines and topical cortisone cream can help with itching and anti-virals such as Zovarax or Famvir may help shorten the length of time of the rash.
Gentle cleansers such as Cetaphil or others formulated for sensitive skin should be used instead of soap. Exposing the rash to short periods of sunshine or the use of UVB phototherapy may speed the recovery of the rash.