It is not uncommon for people to get infections in their feet. An infection is simply an invasion by a microscopic organism that the body has a difficult time fighting off. Infections can be as simple as an athlete's foot fungus or as complicated as a bone infection. Infections in the foot are usually caused by one of three different organism types: bacteria, fungus, or a virus. A fourth type, parasites, are usually only seen in tropical environments and are uncommon in North America.

Fungus is the most common type of foot infection. Various types of fungus cause Athlete's foot as well as nail infections. Fungus is easy to treat in the skin, but harder to treat in the nail. Thriving well in the warm, dark, moist environment of a foot enclosed in a shoe, fungus can be the source of chronic, long term infections. These types of infections are usually superficial to the skin, and rarely pose a significant threat to the foot or leg if treatment is delayed a little.

Bacteria cause the more serious kinds of infection in the foot. There are dozens of bacteria that can infect tissue in the foot, although most infections are grouped into a few common kids of bacteria. Bacteria exist everywhere, and only need a small break in the skin to enter the body, rapidly multiply, and cause destruction of body tissue. People whose immune system is weakened or people with diseases like diabetes are more likely to get infected, especially if one has a wound or steps on an object that punctures the skin. Bacterial infections can be simple matters like blisters and boils, or the infection can spread under the skin and become 'cellulitis'. More serious infections can harm muscle or tendon tissue, and can even cause bone damage if deep enough. Simple infections can be treated with topical medications or antibiotic pills, while more severe cellulitis and deeper infections need intravenous antibiotic medication to effectively kill the bacteria. Not all antibiotics kill all the same bacteria, and the type of bacteria as determined by a culture can determine the best antibiotic to use, especially if the bacteria is resistant to common antibiotics. More serious bacterial infections need surgical intervention, as they can threaten the health of the leg, and can produce toxins that can cause death if not appropriately treated.

Finally, viruses can infect the foot in the form of a wart. Foot warts are common, and are usually a simple infection that poses no health risk like bacteria do. However, foot warts can be painful and may spread around. Treatment is advised because of this. Unfortunately, no topical or oral anti-viral medication currently available is effective against the virus that causes foot warts. Treatment usually centers around the body being stimulated by chemicals applied to the skin to develop an immune response to the virus to destroy it. This will grant the body immunity to the virus that caused the wart, something not possible when the foot infection is due to a fungus or bacteria.