The main reasons for nipple pain in men after exercise are the following: 1. During exercise, especially running and playing ball, nipples and clothing will rub for a long time, especially when wearing tights or sports undershirts made of non-Lycra material, the friction will damage the skin on the nipple surface and even cause nipple bleeding. When men’s nipples are more pointed, they are more likely to have painful nipple discomfort. 2, when men wear new clothes, even without prolonged exercise, there will be nipple pain, because the cotton fabric itself is rougher, or clothing in the process of processing requires chemical treatment, the clothing itself will have chemical residues, chemicals can cause skin allergies or contact dermatitis, some will even lead to Some may even cause hives, blisters, and a burning sensation on the skin, and the nipples may become red, swollen, broken, and bleeding.