Causes
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 when there's a secondary bacterial infection on top of the fungal infection.