Athlete's foot, known as dermatophytosis of the foot or tinea pedis ("foot fungus"), is a common skin infection that affects the feet. You don't have to be an "athlete" to get it.
In North America, 1 in 10 people has athlete's foot. Men tend to be affected more than women, adults more than children. In about 50% of people with athlete's foot, the condition recurs because the fungus spores survive in skin cracks between the toes.
There are three types of athlete's foot: moccasin-type, vesicular or blistered, and interdigital or ulcerative.
Athlete's foot is caused by a fungal infection. The fungi that infect human feet live on the skin, specifically on skin proteins called keratin. These fungi thrive in hot, tropical climates and are recent imports to North America and Europe, brought in by travelers. Wearing tight, non-breathing footwear allows the fungi to flourish and cause athlete's foot. The fungal organisms easily spread from one person to another in moist places where people walk barefoot, such as gym locker rooms and swimming pools. Cuts or blisters on the feet make it easier for these organisms to cause an infection.
Vesicular or blistered athlete's foot is believed to be due to an allergic reaction to fungal organisms, causing blisters to form. Ulcerative tinea pedis occurs in severe cases and can affect large areas, and there's usually a secondary bacterial infection on top of the fungal infection.