Foot odor, for example, is largely due to bacteria that thrive in a moist environment. These same bacteria can also cause pitted keratolysis, a foul-smelling condition in which tiny pits appear on the heels and soles. Continued wearing of wet clothing after exercise also increases the risk of folliculitis, a bacterial infection of the hair follicles. Friction is another common cause of skin problems. Chafing often occurs in areas where skin rubs clothing or another skin surface.
Blisters typically appear in thicker, pressure-bearing areas such as the palms and soles.
Friction from clothing can also cause an irritation, and even bleeding, of the nipples, often called jogger's nipples. Infection can occur in many sports, especially those that involve direct skin contact. Wrestlers are particularly vulnerable to herpes simplex and a similar bacterial infection called impetigo. Infections like impetigo and bacterial folliculitis can also spread via surfaces like pads and handles on weight machines. Finally, cold and sun exposure can cause skin problems or aggravate existing conditions.