Fungus on the feet, commonly called athlete’s foot, is a skin infection caused by fungi that feed on keratin, the protein that makes up your outer layer of skin. It’s one of the most common skin infections worldwide, and it thrives in the warm, moist environment that shoes and socks create. The infection typically shows up as peeling, itchy skin between the toes, but it can also affect the soles, heels, and sides of your feet depending on the type.
What Causes It
Three species of fungus are responsible for most foot infections. They belong to a group called dermatophytes, organisms that have evolved specifically to break down keratin. Your feet are an ideal target because the skin there is thick with keratin, and the space inside your shoes stays warm and damp for hours at a time.
You pick up these fungi by walking on contaminated surfaces: locker room floors, pool decks, shared showers, hotel bathrooms. The fungi shed from infected skin in tiny flakes and can survive on surfaces for extended periods. Once they land on your skin, they produce enzymes that digest the outer layer and establish an infection. People who sweat heavily, wear tight or non-breathable shoes, or have minor skin damage on their feet are especially vulnerable.
Three Types and How They Look
Between the Toes (Interdigital)
This is the most common form. It appears as peeling, white, soggy skin in the web spaces between your toes, most often between the fourth and fifth toes. Itching is the hallmark symptom. The skin may crack or fissure along the edges, which can cause a burning sensation or pain. The infection sometimes spreads from the toe webs onto the sole.
Moccasin Type
This form covers a wider area. You’ll notice dry, thickened, scaly skin on the soles, heels, and sides of the feet, roughly matching the area a moccasin shoe would cover. A border of flaky skin often lines the edge of the foot. The top of the foot is usually spared except near the toes. What makes this type tricky is that it’s often painless and only mildly itchy, so many people mistake it for dry skin and don’t treat it. It tends to be chronic and can persist for months or years.
Blistering (Vesiculobullous)
This is the least common but most uncomfortable type. It produces small, fluid-filled blisters (typically 1 to 3 mm across) on a red, inflamed base, usually on the arch or inner sole of the foot. These blisters are intensely itchy and sometimes painful. They can merge into larger blisters that eventually rupture, leaving raw, oozing skin. This form develops much faster than the other two and is sometimes linked to contact with infected animals.
How Doctors Confirm It
Foot fungus can look a lot like eczema, psoriasis, or contact dermatitis. If there’s any doubt, a doctor can do a simple skin scraping test. They gently scrape a small sample from the affected area, place it on a slide, and add a solution of potassium hydroxide (KOH). This dissolves the skin cells but leaves fungal structures intact, making them visible under a microscope. The test takes minutes and gives a clear answer. If results are inconclusive, a skin biopsy or fungal culture may follow.
Treating Foot Fungus
Most cases respond well to over-the-counter antifungal creams or sprays. Terbinafine cream, one of the most effective options, is applied twice a day. For the interdigital type, treatment typically lasts one to four weeks. For infections covering the sole, plan on at least two weeks of consistent use. Spray formulations work on a similar schedule, generally applied twice daily for about seven days.
Results aren’t instant. It typically takes two to four weeks to see clear improvement. A common mistake is stopping treatment as soon as the skin looks better. You should continue applying the antifungal for at least a week after the rash has visibly cleared to kill any remaining fungus below the surface. If you stop too early, the infection is likely to come back.
When over-the-counter treatments don’t work, or when the infection is widespread or has reached the toenails, a doctor may prescribe oral antifungal medication. The moccasin type, in particular, often resists topical treatment because the thickened skin prevents the medication from penetrating deeply enough. Oral medications work from the inside out and are typically taken for several weeks.
What Happens If You Ignore It
Untreated foot fungus doesn’t just linger. It spreads. The cracked, fissured skin between your toes becomes an entry point for bacteria, which can lead to a secondary bacterial infection called cellulitis. Cellulitis causes redness, swelling, warmth, and pain that extends beyond the original rash, and it can spread into the deeper tissues or bloodstream if left untreated.
Foot fungus also commonly spreads to the toenails, causing them to thicken, discolor, and crumble. Toenail infections are significantly harder to treat than skin infections and can take months to resolve. The fungus can also travel to other body parts. Touching your infected feet and then touching your groin, for example, is a classic route for developing jock itch. Some people develop a fungal infection on one hand (usually the dominant hand used to scratch the feet) while both feet are affected.
Preventing Reinfection
Foot fungus has a high recurrence rate, largely because the fungi are everywhere and your feet keep returning to the same warm, enclosed environment. A few specific habits make a measurable difference.
Wearing socks is genuinely protective. Research on dermatophyte transmission found that socks effectively block fungi from reaching the skin, while thin stockings do not. The material matters: choose socks that wick moisture away from the skin, and change them during the day if your feet sweat heavily. Rotate your shoes so each pair has at least 24 hours to dry out between wears.
Cleaning your footwear helps too. Rinsing sandals and sneakers with water (even cold water) effectively removes fungi from their surfaces. Wiping with a wet towel or using hot water works equally well. Boots are harder to clean thoroughly due to their depth, so pouring cold water inside them is less reliable. Washing socks in warm or hot water is more effective than cold, and turning them inside out before washing ensures the inner surface gets properly cleaned.
After showering in shared spaces, dry your feet thoroughly, especially between the toes. If you’re prone to recurrence, applying antifungal powder to your feet and inside your shoes before putting them on each day adds another layer of protection.