Pityriasis rosea is a harmless, common skin problem that causes a rash. Although it can occur at any age, it is seen most often in those between the ages of 10 and 35.
The cause of pityriasis rosea is unknown. Unlike many other skin conditions, it is not an allergic reaction or caused by a fungus or bacteria. Some experts think it may be caused by a virus. But neither signs of a virus (such as its genetic material) nor symptoms of a viral infection (such as a fever) are found in everyone with pityriasis rosea. Read more about pityriasis rosea.