Athletes foot

Athlete's foot is a skin infection in the foot caused by a fungus. The fungus that causes Athlete foot is called Trichophyton. When the feet, or other areas of the body, stay moist, warm and irritated, this fungus can thrive and infect the upper layer of the skin.

Athlete foot is caused by the ringworm fungus ("tinea" in medical terms). Athlete foot is also called tinea pedis. The fungus that causes Athlete foot can be found on floors and in socks and clothing. The fungus can be spread from person to person by contact with these objects. However, without proper growing conditions (a warm, moist environment), the fungus will not infect the skin. Up to 70% of the population will have athletes foot at some time during their lives.


Causes:
The most common fungi causing tinea pedis are Trichophyton rubrum and T. mentagrophytes. 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.

Symptoms:
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 armpits, knees, elbows, and 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) for an infection of the groin).
Tinea pedis most often manifests between the toes, with the webspace between the fourth and fifth digits most commonly afflicted.

Diagnosis:
A microbiological culture of skin scrapings can be used in diagnosis, but the process takes several weeks and can often give false negative results.
Tinea infections are sometimes misdiagnosed as atopic dermatitis or allergic eczema, underscoring the importance of a KOH (potassium hydroxide) preparation or microbiological culture being performed before treatment is initiated.
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 and histological examination of the tissue performed.

Treatment:
The fungal infection is often treated with topical antifungal agents, which can take the form of a spray, powder, cream, or gel. The most common ingredients in over-the-counter products are Miconazole nitrate and Tolnaftate. Terbinafine, marketed as Lamisil is another over-the-counter drug. There exists a large number of prescription antifungal drugs, from several different drug families. These include ketaconazole, itraconazole, naftifine, nystatin, caspofungin. Studies show that Allylamines (Terbinafine, Amorolfine, Naftifine, Butenafine) cure slightly more infections than azoles (Miconazole, ketaconazole, Clotrimazole, itraconazole, sertaconazole, etc).