The main cause of foot odor is the breakdown of bacteria in sweat, according to the National Health Service. Glands in the feet produce sweat to keep the skin moist.
It is normal for the feet to sweat, but some people are more prone to developing foot odor than others. Poor hygiene may be a factor, especially if a person does not wash his feet regularly or change socks frequently. Footwear may also contribute to smelly feet. Certain types of shoes cause the feet to sweat more than usual. If the sweat does not evaporate, the skin stays moist. The bacteria responsible for foot odor thrive in damp, dark conditions, reports the NHS.
Smelly feet may also be a sign of an underlying medical condition or hormonal shift. Foot odor is common in pregnant women and teenagers because of all the hormonal changes they experience. A condition called hyperhidrosis causes excessive sweating. MedlinePlus says the sweat glands seem to be overactive in people who have hyperhidrosis.
There are several ways to combat foot odor. Washing feet daily, wearing socks with closed shoes and wearing shoes that allow the feet to breathe may be enough to prevent smelly feet, according to the American Academy of Podiatric Practice Management. If the odor persists, antibacterial ointments and nonmedicated powders may be used to dry up excess moisture and eliminate the bacteria responsible for foot odor.