Purple patches on the calves can be considered as manifestations of skin lesions such as allergic purpura, senile purpura or venous stasis purpura. 1. Allergic purpura: its occurrence can be related to a variety of factors such as upper respiratory tract infections such as viral infections or drugs (such as penicillin), mycoplasma infections, pregnancy or food, etc. It can appear in the skin of the extensor side of the limbs and other places of the skin in a small and scattered petechiae, which can be fused into a large patch of bruises. 2. Elderly purpura: When the aged and exposed parts are exposed to sunlight for a long time, due to the skin relaxation and thinning, the blood vessels may rupture and bleed under the effect of slight trauma, forming dark purple petechiae or ecchymoses. 3. Venous purpura: it is thought to be related to varicose veins of the lower limbs, the disease can occur when standing for a long time, sagging calves, sedentary, etc. Purpuric macules can be seen in the lower third of the calf, varicose veins and venous tumors, which can be merged into patches after a long time, presenting purple, yellow and brown, and itching can be found. The appearance of more purple plaques on the lower legs, it is recommended to consult a doctor in time, after a clear diagnosis, standardized treatment.