Flat warts are caused by human papilloma virus infection of the skin mucous membranes, usually not affected by the environment, dry environment will still grow. Flat warts are a kind of warts, a kind of benign superfluous organism, for the virus infection caused by the disease, there is a certain degree of contagious. The virus enters the cells through tiny breaks in the skin and mucous membranes, leading to abnormal differentiation and proliferation of the epithelial cells, and eventually forming a superfluous organism. This process occurs in the body, usually not affected by the environment, so the virus infection, even in a dry environment, flat warts can still grow. Flat warts are a self-limiting disease, most of them will disappear over time, but because of the infectiousness and recurrence, it is recommended that flat warts patients actively seek medical treatment and follow the doctor’s instructions.