The feet are the parts of the body that are most commonly infected by certain fungi called dermatophytes.1 When this happens, the result is called tinea pedis or athlete’s foot.
Athlete’s foot, from acute vesicular to chronic, is a very common problem that's experienced by up to 70% of the population at some point in life.
Who Is Most at Risk?
Athlete’s foot is common in adult males and uncommon in women.2 Athlete’s foot can also affect children before puberty, regardless of sex.
Athlete’s foot seems to occur most often in people who have immune systems that predispose them to infection, no matter how many precautions they take.3
Once an athlete's foot infection is established, the person becomes a carrier and is more susceptible to recurrences and complications.
Athlete’s foot is divided into three categories:
Chronic interdigital athlete’s foot
Chronic scaly athlete’s foot (moccasin-type)4
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 webbed space between the fourth and fifth toes.5
Tight-fitting, non-porous shoes compress the toes, creating a warm, moist environment in the webbed spaces.6 Many times, the infecting fungus interacts with bacteria, causing a more severe infection that extends onto the foot.
In chronic interdigital athlete’s foot, itching is typically most intense when the socks and shoes are removed.
Chronic Scaly (Moccasin-Type) Athlete’s Foot
This type of athlete’s foot is caused by Trichophyton rubrum.7 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.8
Chronic scaly athlete’s foot is often seen in people who have eczema or asthma and 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.9 It often originates in people who have a chronic interdigital toe web infection.
Acute vesicular athlete’s foot is characterized by the sudden onset of painful blisters on the sole or top of the foot.10
Another wave of blisters may follow the first and may also involve other 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—it's called an id reaction. This type of athlete’s foot is also known as “jungle rot,” a historically disabling problem for servicemen fighting in warm, humid conditions.
Diagnosing the Infection
Athlete’s foot is diagnosed by a clinical exam. A doctor usually performs something called a KOH test.11 A positive KOH test confirms the diagnosis, but a negative KOH test does not mean that a person does not have athlete’s foot. Fungal elements can be difficult to isolate in interdigital and moccasin-type athlete’s foot.
KOH Prep Test to Diagnose Fungal Skin Infections
Mild cases of athlete’s foot, especially interdigital toe web infections, can be treated with topical antifungal creams or sprays such as tolnaftate12 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 itraconazole13
for two to six months. All oral antifungal medications can affect the liver; therefore, blood tests should be performed monthly to evaluate liver function.