The feet are the most common area infected by certain fungi called dermatophytes, causing tinea pedis or athlete’s foot. Athlete’s foot is a very common problem experienced by up to 70% of the population at some time in their life.
Athlete’s Foot Demographics
Athlete’s foot is common in adult males, but uncommon in women. Athlete’s foot can also affect children before puberty, regardless of sex. Athlete’s foot seems to occur most often in people who have some characteristic of their immune system which predisposes them to infections regardless of the precautions they take to prevent infection. Once an infection is established, the person becomes a carrier and is more susceptible to recurrences and complications.
Athlete’s Foot Types
Athlete’s foot is divided into three categories:
- Chronic interdigital athlete’s foot
- Chronic scaly athlete’s foot (moccasin type)
- Acute vesicular athlete’s foot
Chronic Interdigital Athlete’s Foot
This is the most common type of athlete’s foot. It is characterized by scaling, maceration, and fissures most commonly in the web space between the 4th and 5th toes. Tight-fitting, non-porous shoes compress the toes, creating a warm, moist environment in the web spaces. Many times the infecting fungus interacts with bacteria causing a more severe infection that extends onto the foot. With this type of athlete’s foot, itching is typically most intense when the socks and shoes are removed.
Moccasin Type Athlete’s Foot
This type of athlete’s foot, also known as moccasin-type, is caused by Trichophyton rubrum. This dermatophyte causes dry, scaling skin on the sole of the foot. The scale is very fine, and silvery, and the skin underneath is usually pink and tender. The hands may also be infected, although the usual pattern of infection is two feet and one hand, or one foot and two hands. This type of athlete’s foot is often seen in people with eczema or asthma. It is associated with fungal nail infections which may lead to recurrent skin infections.
Acute Vesicular Athlete’s Foot
This is the least common type of athlete’s foot, caused by Trichophyton mentagrophytes. It often originates in people who have a chronic interdigital toe web infection. This type of athlete’s foot is characterized by the sudden onset of painful blisters on the sole or top of the foot. Another wave of blisters may follow the first and may also involve remote sites of the body such as the arms, chest, or sides of the fingers. These blisters are caused by an allergic reaction to the fungus on the foot and are known as an id reaction. This type of athlete’s foot is also known as “jungle rot,” a historically disabling problem for servicemen fighting in warm, moist, humid conditions.
Diagnosis of Athlete’s Foot
Athlete’s foot is diagnosed by clinical exam and performing a KOH test. A positive KOH test confirms the diagnosis, but a negative KOH test does not mean a person does not have athlete’s foot. Fungal elements can be difficult to isolate in interdigital and moccasin type athlete’s foot.
Treatment of Athlete’s Foot
Mild cases of athlete’s foot, especially interdigital toe web infections, can be treated with topical antifungal creams or sprays such as tolnaftate, or lotrimin. Topical medications should be applied twice a day until the rash is completely resolved. More serious infections and moccasin type athlete’s foot should be treated with oral antifungal medications such as terbinafine or itraconazole for 2 to 6 months. All oral antifungal medications can affect the liver; therefore, blood tests should be performed monthly to evaluate liver function.