Athlete’s foot (also known as ringworm of the foot and tinea pedis) is a fungal infection of the skin that causes scaling, flaking, and itch of affected areas, is caused by fungi in the genus Trichophyton. While it is typically transmitted in moist communal areas where people walk barefoot, such as showers or bathhouses, the disease requires a warm moist environment, such as the inside of a shoe, in order to incubate. Because of this the fungus only affects approximately 0.75% of habitually (always) barefoot people.

Although the condition typically affects the feet, it can infect or spread to other areas of the body, including the groin, particularly areas of skin that are kept hot and moist, such as with insulation, body heat, and sweat in a shoe, for long periods of time. While the fungus is generally picked up through walking barefoot in an infected area or using an infected towel, infection can be prevented by remaining barefoot as this allows the feet to dry properly and removes the fungus’ primary incubator – the warm moist interior of a shoe.  Athlete’s foot can be treated by a number of pharmaceuticals (including creams) and other treatments, although it can be almost completely prevented by never wearing shoes, or wearing them as little as possible.

Signs and symptoms

Pale, flaky & split skin of athlete’s foot in a toe

Athlete’s foot causes scaling, flaking, and itching of the affected skin. Blisters and cracked skin may also occur, leading to exposed raw tissue, pain, swelling, and inflammation. Secondary bacterial infection can accompany the fungal infection, sometimes requiring a course of oral antibiotics.

The infection can be spread to other areas of the body, such as the groin, and usually is called by a different name once it spreads, such as tinea corporis on the body or limbs and tinea cruris (jock itch or dhobi itch) for an infection of the groin. Tinea pedis most often manifests between the toes, with the space between the fourth and fifth digits most commonly afflicted.

Some individuals may experience an allergic response to the fungus called an “id reaction” in which blisters or vesicles can appear in areas such as the hands, chest and arms. Treatment of the fungus usually results in resolution of the id reaction.

Diagnosis

Microscopic view of cultured athlete’s foot fungus

Athlete’s foot can usually be diagnosed by visual inspection of the skin, but where the diagnosis is in doubt direct microscopy of a potassium hydroxide preparation (known as a KOH test) may help rule out other possible causes, such as eczema or psoriasis.A KOH preparation is performed by taking skin scrapings which are covered with 10% to 20% potassium hydroxide applied to the microscope slide; after a few minutes the skin cells are degraded by the KOH and the characteristic fungal hyphae can then be seen microscopically, either with or without the assistance of a stain. The KOH preparation has an excellent positive predictive value, but occasionally false negative results may be obtained, especially if treatment with an antifungal medication has already begun.

If the above diagnoses are inconclusive or if a treatment regimen has already been started, a biopsy of the affected skin (i.e. a sample of the living skin tissue) can be taken for histological examination.

A Wood’s lamp, although useful in diagnosing fungal infections of the scalp (tinea capitis), is not usually helpful in diagnosing tinea pedis, since the common dermatophytes that cause this disease do not fluoresce under ultraviolet light. However, it can be useful for determining if the disease is due to a nonfungal afflicto