The cause of pityriasis rosea is not yet clear. There are infectious (fungal, bacterial), focal, metabolic reaction, metabolic disorder and so on many kinds of theories, from this disease onset process, seasonal influence, rarely recurrence, etc., suggest that may be related to infectious factors, at present tend to be viral infection.
The onset of pityriasis rose initially is in the trunk appears a round light red spot, is called “mother spot”. The mother spot continuously expands, even can reach the egg size. After that, smaller erythematous spots appear one after another in the trunk. Most of the rashes are oval in shape, and their long axis is in line with the skin texture.
The natural course of the disease is one month to two months, and if it does not itch, no treatment can be needed. Liu Houguang, Department of Dermatology and Venereology, Xiamen Third Hospital