Infections of the feet can be fairly common, and range from mild to extremely dangerous. There are four main types of infections that can occur in the feet: fungal, viral, bacterial, and those that develop in diabetic foot ulcers.

Fungal infections:

Feet can become infected by various fungi either directly or indirectly. For instance, dermatophytes are fungi responsible for the athlete’s foot infection. Direct exposure with dermatophytes can occur from skin-to-skin contact with an infected person, or by exposing your feet to wet, damp, and dark environments where fungi are living: locker rooms, pool areas, communal showers and bathing areas. It can also be spread by contact with towels, shoes, floors, or personal grooming instruments that are carrying the fungi. This type of infection produces a red, scaly, itchy rash on the feet and between the toes, which can peel, blister or crack.

Dermatophytes can also be responsible for fungal toenail infections, (onychomycosis). This type of infection can occur underneath one or more toenail(s), and produce symptoms such as thickened, discolored, crumbly, painful, brittle, or smelly nails. Fungal toenail infections can occur if you already have athlete’s foot, have suffered a nail injury, have a weakened immune system, have hyperhidrosis (overly sweaty feet), poor circulation, or if you contract it at a nail salon that doesn’t disinfect their equipment properly, or you don’t air out damp shoes before wearing them again. Fungal toenail infections are stubborn and difficult to treat with over-the-counter products because the fungi can embed themselves deep within the many layers making up the nail, or even completely under the nail—in the nail bed. 

Viral infections:

When particular strains of the human papillomavirus (HPV) enter the body through cracks or breaks in the skin of the foot, it can cause plantar warts to develop on the bottom of the feet (or sometimes on the toes). These are flat, hardened patches of skin that sometimes have a visible “dot” in the center (tiny, dried blood vessels) and may grow as singular warts or clusters of warts (called mosaics). Since they are on the sole of the feet, pressure placed on the warts from walking can make them quite painful. These warts can spread easily from one part of your foot to another, and also from one person to another.

A less common viral infection that mostly affects young children is called hand, foot, and mouth disease (HFM). This is caused by the coxsackievirus and can produce symptoms such as a rash on the bottom of the feet and hands, as well as mouth sores and fever.

Bacterial infections:

Injuries of the skin of the feet, (i.e., cuts, scrapes and blisters) may allow different bacterial infections to set in. 

Erythrasma, caused by corynebacterium minutissimum causes swollen, itchy, red or brown patches between the toes or in the folds of the skin, which may sometimes have pus. Erythrasma can be mistaken for athlete’s foot. Oral or topical anti-bacterial medicines are used to treat this condition.

Staphylococcal bacteria that has entered the body can cause soft tissue in the feet to become infected, inflamed, and painful. White blood cells that rush to the area to kill the infection wind up killing surrounding healthy tissue, creating a hole which becomes filled with pus. This is called an abscess.

Both streptococcus and staphylococcus bacteria can cause cellulitis in the feet when a break in the skin allows these microorganisms to enter. Cellulitis can make the skin on the feet and legs swollen, painful, red, hot and blistered. Glands can also become swollen and painful.

Diabetic wound infections:

Any small cut, scrape, abrasion, or break in the skin of the feet can develop into a wound if you have diabetes. Complications from diabetes can make these wounds very difficult to heal, which may lead to them becoming ulcers. Diabetic foot ulcers can become infected with various bacterial microorganisms, which is a very serious condition. Diabetic foot infections will cause the area surrounding the actual wound to be red, painful, tender, numb, and it may seep pus. There also may be gangrenous tissue present.

If you have any symptoms that lead you to believe you have an infection in your feet or lower legs, make an appointment as soon as possible with your podiatrist—particularly if you have diabetes, a fever, or the infected foot is red, feels warm to the touch, or is discolored with red or white streaks.