The cause of pityriasis rosea, so far not completely elucidated, the current study that may have a relationship with the following factors: 1, may have a relationship with infection, because the prodromal period of pityriasis rosea, may have a history of upper respiratory tract infection, so, viral infection may have some connection with pityriasis rosea. 2, drug factors, many drugs can clearly induce pityriasis rosea and pityriasis rosea-like rash, such as vaccine, metronidazole , barbiturates, interferon, etc., can clearly induce pityriasis rosea-like rash, characterized by more extensive damage, large lesions, treatment difficulties. Other factors, such as patients with seborrheic dermatitis, acne, etc., the incidence of pityriasis rosea is significantly higher. At the same time, the spirit is in the high tension state, suffers from the pityriasis rosea rate is obviously higher, indicates the pityriasis rosea, also is the certain physical and mental disease.