Article: Athlete's foot

Athlete's foot or tinea pedis is a fungal infection of the skin, usually between the toes, caused by parasitic fungi.

Causes

The body normally hosts a variety of saprotrophic microorganisms, including bacteria and fungi. Some of these are useful to the body. Pathogenic or disease causing organisms or the overgrowth of saprotrophic ones can multiply rapidly and cause infection. Athlete's foot is a layman's description of a skin fungal infection. Fungal infections of the skin are called dermatophytosis. Dermatophytes may be spread from other humans (anthropophilic), animals (zoophilic) or may come from the soil (geophilic). Anthropophillic dermatophytes are restricted to human hosts and produce a mild, chronic inflammation. Zoophilic organisms are found primarily in animals and cause marked inflammatory reactions in humans who have contact with infected cats, dogs, cattle, horses, birds, or other animals. Geophilic species are usually recovered from the soil but occasionally infect humans and animals. They cause a marked inflammatory reaction, which limits the spread of the infection and may lead to a spontaneous cure but may also leave scars. Infections or infestations occur when dermatophytes grow and multiply in the skin.

Classification by area

When these infections occur on the feet they are called tinea pedis, on the head, tinea capitus, the bearded areas, tinea barbae, and the smooth skin areas tinea corporis. In addition to dermatophytes, other classes include yeasts such as Candida albicans.

When the infection occurs in any fold of skin, it is called an intertrigo. An intertrigo can occur when a fold of skin, typically between the toes or fingers, but also in the underarm area, beneath pendulous breasts or in the groin area traps moisture making an ideal growth field for the fungal invader.

Deeper invasion of the tissue of the foot, so called madura foot or maduramycosis can be caused by yeast. The lumps are called mycetoma. These infections are limited to the skin but do destroy local tissues. The infections usually occur in the subtropic and tropic regions but are sometimes seen in populations with impaired immunity such as the homeless and those with AIDS. The disease is named after the region in India where it was first described in 1842.

Other fungal infections such as coccidioidomycosis and aspergillosis can have skin manifestations but are usually systemic infections associated with the lungs.

Growth environment

Growth of the athlete's foot fungus is promoted by a dark, warm, moist environment such as that found inside shoes. The fungi persist for a long time in the environment, facilitating transmission of the disease in communal areas such as locker rooms and showers.

Symptoms

Intertrigo between toes

Athlete's foot causes scaling and itching of the affected skin. Blisters and cracked skin may also occur, leading to exposed raw tissue, pain, swelling, and inflammation. Despite its name, the infection can be spread to other areas of the body, such as the armpits and the groin.

Treatment

The infection is often treated with topical antifungal agents such as miconazole, itraconazole, terbinafine and a keratolytic such as salicylic acid. Topical agents only clear the infection about 30% of the time and provide mycologic cures (absence of organisms) less than 15% of the time. The time line for cure may be long, often 45 days or longer. However, because the itching associated with the infection subsides quickly, patients may not complete the courses of therapy prescribed. Washing socks, underwear and bed clothes at 60C or 140F will also help prevent any reinfection.

Some topical applications such as Castellani's Paint, often used for intertrigo, work well but in small selected areas. Carbol Fuscin Red dye used in this treatment like many other vital stains is both fungicidal and bacteriocidal; however, because of the staining are cosmetically undesirable. For many years gentian violet was also used for interdigital and other bacterial and fungal infections.

Oral treatment with griseofulvin was begun early in the 1950s. Because of the tendency to cause liver problems and to provoke aplastic anemia the drugs were used cautiously and sparingly. Over time it was found that those problems were due to the size of the crystal in the manufacturing process and microsize and now ultramicrosize crystals are available with few of the original side effects. Oral treatment provides long lasting mycologic cure.

If the fungal invader is not a dermatophyte but a yeast, other medications such as diflucan may be used. Typically diflucan is used for candidal vaginal infections moniliasis but has been shown to be of benefit for those with cutaneous yeast infections as well. The most common of these infections occur in the web spaces (intertriginous) and at the base of the fingernail or toenail. The hall mark of these infections is a cherry red color surrounding the lesion and a yellow thick pus.

Remedies and folklore

Traditional remedies for athlete's foot include tea tree oil or crocodile oil in a topical application on the affected area. Users report instant relief from itching allowing lesions to heal. Proponents of urine therapy claim that urine is very effective at killing athlete's foot. Urea, the "active ingredient" in urine, is already used in many drugs and treatments made by pharmaceutical companies to treat athlete's foot. This controversial treatment method recommends urinating on the infected area once a day in the shower. According to supporters, urine therapy not only kills existing fungi, it prevents new fungi from growing in the infected area.

One biochemist states that urea is only used to soften the outer layers of skin so that antifungal drugs can reach fungi below the surface, and that the urea must be concentrated and applied for a long period of time in order to be effective. [1] According to another article about high-concentration urea cream, the compound is used to "dissolve proteins and [as a] denaturant. The ability of urea to macerate [tissue] has been attributed to a 'proteolytic effect', but others attribute the maceration to the hydrating properties of urea." [2] This use requires a high concentration of urea, up to 40%, and extended exposure. Urea itself without the presence of an additional antifungal drug is not referred to in scholarly literature as having antifungal properties. Thus, it is unlikely that urinating on one's feet in the shower will significantly improve a case of athlete's foot.

Also the use of horse liniment (such as Absorbine Jr.) works well because of the menthol and wormwood contained in the liquid substance, though when applied to very dry or cracked areas of skin it can be very painful. Applying this three times a day for one month can cure most fungal infections; continually applying it once a day (usually at night before bedtime), can work as a preventative.