why do men's nipples bleed when they run

Men's nipples can bleed when they run due to a condition called "runner's nipple," which is caused by friction and chafing between the nipples and clothing during running. The repetitive rubbing of the shirt fabric against the nipples, especially in longer runs, leads to irritation, rawness, and sometimes bleeding. Factors like moisture from sweat, cold weather causing nipples to become erect, and rough or cotton fabrics increase the likelihood of this injury. Runner's nipple is more common among long-distance runners and can be painful, causing red, dry, irritated skin that may bleed. The condition can worsen if infections or rashes develop on the raw skin. Preventative measures include wearing moisture-wicking, well-fitting shirts, applying lubricants like petroleum jelly, using adhesive tape or bandages on nipples, and running shirtless if possible. In summary, men's nipples bleed when they run primarily due to friction and chafing caused by clothes rubbing repeatedly against the sensitive nipple skin, especially under sweaty or cold conditions.