The causes of purple spots on legs include trauma, allergic purpura, fire-excited erythema and so on. According to different causes, drug treatment and general treatment can be chosen. Purple spots caused by allergic purpura have the possibility of recurrence. 1. Trauma: local blood vessels rupture after trauma to the legs, and the collection of bruises can lead to the appearance of purpura on the skin. Usually, it fades gradually after a period of time, and it can also be promoted by applying ice in the early stage and hot compresses in the later stage to promote the fading of purpura. 2. Anaphylactic purpura: Before the onset of the disease, there are often upper respiratory tract infection, low fever, general malaise and other prodromal symptoms, followed by the appearance of red papules, usually within 24 hours to develop into the tip of the needle to soybean-sized purpura, there can also be petechiae. Most of the disease is self-limiting, and oral glucocorticosteroids such as prednisone can be taken if necessary. 3. Fire-excited erythema: fire-excited erythema is a reticular erythema-like damage caused by long-term repeated exposure to heat. Usually no treatment is needed, and it will be cured after stopping the fire. There may be other reasons leading to purple spots on legs. If you want to cure purple spots on legs, you need to clarify the causes of purple spots and treat them according to the causes. It is recommended that patients go to the hospital in time and do not use drugs without authorization.