Athlete's foot is a fungal infection of the skin, usually between the toes, caused by parasitic fungi.
Causes
The body normally hosts a variety of saprophytic microorganisms, including bacteria and fungi. Some of these are useful to the body. Pathogenic or disease causing organisms or the overgrowth of saprophitic 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 the smooth skin areas tinea corporis. In addition to dermatophytes, other classes include yeasts such as Candida albicans. 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 coccidiomycosis , psittacosis 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
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.
When the infection occurs between the toes or fingers or in any fold of skin, it is called an intertrigo.
Treatment
The infection is often treated with topical antifungal agents such as miconazole, itraconazole or terbinafine. Topical agents only clear the infection about 30% of the time and provide mycologic cures (absence of organisms) less then 15% of the time. Because the time line for cure may be long, often 45 days or longer, but the itching associated with the infection subsides quickly, patients may not be completing courses of therapy. 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 which exudes from them.
Remedies and folklore
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. However, at least 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] The existence of prescription creams such as Vanamide® which are indicated for dry or rough skin and consist of up to 40% urea supports this claim. Thus, it is unlikely that urinating on one's feet in the shower will significantly improve a case of athlete's foot.
See also
External links
Last updated: 05-07-2005 08:32:47
Last updated: 05-13-2005 07:56:04
