In medicine, redness refers to capillary dilatation. The appearance of capillary dilatation on the skin of the legs may be related to genetic factors, trauma, physical factors, infections and other reasons. 1. Genetic factors: capillaritis has a certain genetic susceptibility, if parents or people in the family suffer from capillaritis, it will lead to an increase in the chances of the next generation of the disease. 2. Trauma: If the skin of the legs has been traumatized or surgically incised, capillarodilatation may occur in the traumatized area. 3. Physical factors: If the skin of the legs is subjected to cold or hot stimulation for a long time, it will lead to a deterioration in the tolerance of the capillaries, and capillarodilatation may occur. 4. Infection: Capillaritis may be related to EBV infection. For patients with capillary dilatation of the skin on the legs, it is recommended to go to a regular hospital for examination to clarify the cause of the disease.