Excessive moisture
Excessive moisture appears after doing sport or hard work. The wet skin, caused by sweat, promotes the proliferation of skin bacteria causing irritation.
An example of a bacteria living in moist areas causes Foot Odor, Athlete's foot and Jock itch. Wearing socks made out of absorbent synthetic will prevent foot odor from appearing. When sweating, try to change your clothes as soon as possible, in order to prevent skin bacteria from irritating your skin.
Other types of skin irritations while doing sport: