A large number of brown spots on the calves of young people may be caused by pigmentation, purpura, seborrheic keratosis and other diseases. 1. pigmentation: eczema, dermatitis, folliculitis and other diseases have appeared on the calf before, and after recovery from treatment, local temporary pigmentation may lead to brown spots on the calf. 2. Purpura: Purpura is caused by the exudation of red blood cells from blood vessels to the skin, connective tissues and mucous membranes, and is a type of subcutaneous hemorrhage. Resulting in double lower limbs, upper limbs, skin bruises or bruises, no pain when pressed with the hand, the color does not go down for a long time can be a brown spot, which can gradually subside, or recurring episodes. 3. Seborrheic keratosis: seborrheic dermatitis, also known as age spots, are benign tumors of the skin, easily occurring in the limbs, trunk and other parts of the body, resulting in local appearance of clear boundaries, the size of the flat papules or plaques. In addition to this, flat warts, pigmented lichenoid dermatitis, may also lead to the local appearance of a large number of brown spots. It is recommended not to blindly use drugs, you can first go to the hospital dermatology department for examination, clear diagnosis, for the cause of the treatment.