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 have 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 travellers. 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.
Athlete's foot usually forms between the fourth and fifth (smallest) toes or third and fourth toes, producing skin cracking, white and soggy toes, scaling, and itchiness. The infection can spread to the soles of the feet. It's made worse by sweaty feet and wearing tight socks or shoes that stay in moisture. If a bacterial infection sets in on top of it, the skin will ooze, burn, and smell.
Moccasin-type athlete's foot doesn't cause itching or inflammation. The entire sole and heel become dry and flaky with loose, white scales that appear in a moccasin-like pattern. Sometimes the toenails can also become infected, which makes it more difficult to treat.
People with vesicular or blistered athlete's foot suffer from sore, fluid-filled blisters that occur between the toes and on the arch and sides of the foot. These blisters form in response to an allergic reaction to the fungi causing the athlete's foot.
Interdigital tinea pedis is the most common type and presents as maceration (softened tissue caused by soaking) and scales in the web spaces between the toes. Ulceration develops when a secondary bacterial infection occurs. Symptoms include painful ulcers between the toes, which often take a long time to heal.
Tinea pedis can lead to foot or leg infections (cellulitis). This can be particularly worrisome in people who have diabetes or chronic vascular diseases.