Sweat is a mixture of water, salt and other minerals. When the water evaporates, only salt and minerals remain on the skin, usually on the nipples. Why on them? Because they are located just in the center of the zone of increased sweating and protrude above the skin surface.
"When you run, your T-shirt inevitably contacts the skin. If your skin is covered with salt, even the softest T-shirt fabric seems worse than sandpaper," says Dr. Bright, adding that it is a common case for male beginners (because men sweat more than women, and beginners also spend more time to overcome the same distance).
Due to constant friction, the skin around the nipples becomes inflamed and starts bleeding. Women may also face this problem.
"The skin around the nipples is very delicate and it's easy to damage it," continues Dr. Bright, athletic director of the Ohio marathon. "Women are also at risk of rubbing their nipples into blood, running without a sports bra or wearing a poorly matched or a cotton bra."
Running tip: Drink enough liquid. It sounds strange, but it's the best thing you can do. Water is necessary to maintain the process of sweating.
"As soon as you stop sweating, you are left alone with salt on the skin," says Dr. Bright.
Men may cover their nipples with adhesive plasters, and women can use moisturizers and properly chosen sports bras.