Cause
Jogger's nipple is caused by friction from the repeated rubbing of a t-shirt or other upper body clothing against the nipples during a prolonged period of exercise.
The condition is suffered mainly by runners. Long-distance runners are especially prone, because they are exposed to the friction on the nipple for the greatest period of time. However, it is not only suffered by athletes; the inside of a badge, a logo on normal items of clothing, or breastfeeding can also cause the friction which results in this condition.
Read more about this topic: Fissure Of The Nipple