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This article written by Nikki Levin, MD, PhD
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What are the symptoms of athlete’s foot?
Athlete’s foot may be itchy, painful, or have no symptoms at all. When the skin is chronically moist due to air-tight footwear, there may also be an unpleasant odor. In severe or inflammatory cases of athlete’s foot -- or when a bacterial infection is also present -- the skin may be very sore and uncomfortable.
What does athlete’s foot look like?
There are three main types of athlete’s foot. Each type has a different appearance and symptoms, though any two or even all three types may occur together:
1. Interdigital athlete’s foot is an infection of the web spaces between the toes, particularly between the 4th and 5th toes. The skin appears moist and waterlogged (Figure 2) and is often itchy. This is the most common kind of athlete's foot.
Figure 2. Interdigital athlete’s foot with typical moist peeling skin between the toes.
2. Moccasin type athlete’s foot is a rash involving the bottoms of the feet, the heels and the sides of the feet (Figure 3). As its name suggests, this type of athlete’s foot involves the area of the foot that would be covered by a moccasin, although it may extend onto the top of the foot (Figure 4) and in severe cases may cover the entire foot (Figure 5). It has a dry scaly (flaky) appearance. The skin may be red or flesh-colored and the scale may range from white to silver. This type of athlete’s foot is rarely itchy or uncomfortable.
A clue to the presence of athlete’s foot is the presence of co-existing fungal toenail infection. The toenails may appear thickened and discolored (Figures 4, 5, 6, and 7), and have crumbly material underneath the nail, which is partially separated from the underlying skin.
Some people with athlete’s foot have a co-existing fungal infection on one of their hands, in the so-called “Two feet- one hand tinea” syndrome. Thus, it is important to examine the hands in people with athlete’s foot, and to treat them as well, if they appear red and scaly.
Figure 3. Moccasin type athlete’s foot showing scaling on the sole and side of the foot. Photograph courtesy of Dr. Amit Garg.
Figure 5. A severe case of athlete’s foot involving nearly the entire foot. Note also the thickened discolored toenails, indicative of a fungal toenail infection. Photograph courtesy of Dr. Mary E. Maloney.
Figure 6. Fungal infection of the toenail (onychomycosis). An arrow indicates the affected toenail, which is thickened and discolored.
Figure 7. A case of inflammatory athlete’s foot, showing redness, oozing, and crusting, especially of the first and fourth toes. Note that fungal toenail infection is also present. Photograph courtesy of Victoria L. Lazareth, NP.
How is athlete’s foot diagnosed?
When someone has a red, scaly, itchy rash on the soles of the feet or between the toes, the diagnosis of athlete’s foot is usually straightforward. Nonetheless, there are several other conditions that can appear similar to athlete’s foot, so physicians may need to confirm the diagnosis with one of the following diagnostic tests:
- Potassium hydroxide preparation: In this test, the physician uses a sharp blade or glass slide to scrape off dead skin cells from the edge of the rash. The dead skin cells are collected onto a microscope slide, treated with a solution of potassium hydroxide and heated to digest the cells, and then examined under a microscope. Sometimes, a dye is added to the potassium hydroxide solution to facilitate visualization of the fungal elements. The physician examines the slide, looking for branching filaments of the fungus (Figure 9). This is the most rapid and inexpensive test to identify dermatophyte fungi, although it occasionally gives false negative results when an individual has already partially treated their athlete’s foot and few fungal cells are still present.
- Fungal culture: The physician scrapes dead skin cells from the edge of the rash and sends them to a microbiology laboratory. There, the material is applied to fungal culture medium. By the appearance of the fungal colonies that grow and their growth characteristics, it is possible not only to show that a fungus was present, but also determine the species. However, this method takes two to three weeks to give results and also frequently gives false negative results. Furthermore, it is not usually necessary to know the exact species in order to treat athlete’s foot.
- Skin biopsy: When a case of athlete’s foot looks very similar to other skin diseases and a potassium hydroxide preparation is negative or inconclusive, physicians will sometimes take a small sample of skin for pathologic examination. Under local anesthesia, a small plug of skin called a punch biopsy is removed and fixed in formalin. Pathologists examine the skin after slicing it into thin sections and staining it with dyes that highlight fungal elements. This method is most expensive (and slightly uncomfortable for the patient), but it does usually give definitive diagnostic results.
Figure 9. A potassium hydroxide preparation demonstrating branching fungal hyphae typical of a dermatophyte fungus. The arrows point to fungal elements.
What other conditions could be confused with athlete’s foot?
Athlete’s foot may be confused with several skin conditions, but they can usually be distinguished based on the appearance of the rash or diagnostic testing:
- Dyshidrotic eczema: this itchy rash occurs on the palms and soles, often in people who have a history of atopic dermatitis (eczema). It appears as tiny water blisters that look like tapioca pearls. Unlike athlete’s foot, it responds to corticosteroid creams, rather than to antifungal preparations.
- Contact dermatitis: this rash occurs as an irritant or allergic reaction to a chemical or other product that has contacted the skin, for example rubber products present in shoes. Unlike athlete’s foot, it usually affects the tops of the feet more than the soles and it responds to corticosteroid creams.
- Psoriasis: this rash may affect the palms and soles with red scaly skin or pustules, but it usually will also be found on the knees, elbows, buttocks, or scalp -- allowing distinction from athlete’s foot.
- Erythrasma/pitted keratolysis: These common skin infections with Corynebacteria and Micrococcus bacteria may appear as a red scaly rash or tiny pits in the soles of the feet. They respond to topical antibiotic preparations rather than to antifungals.
- Dry skin: Especially in the winter, people may have dry, scaly skin on the soles of the feet in the absence of any fungal infection.
Athlete’s foot can be distinguished from each of the conditions listed above by doing a skin scraping and potassium hydroxide preparation (Figure 9) or fungal culture. These tests would be expected to show evidence of fungi in athlete’s foot and be negative in all the other diseases.
How can one prevent athlete’s foot?
The best way to prevent athlete’s foot is to keep the feet clean and dry and avoid exposure to athlete’s foot fungus. The following measures may be helpful:
- Carefully drying the feet and spaces between the toes after bathing
- Applying a drying powder to the feet or shoes daily
- Changing socks frequently if they become damp
- Avoiding occlusive (non-breathable) footwear
- Wearing sandals or other open footwear when possible
- Avoiding walking barefoot in locker rooms and communal showers where fungal spores may be found
- Avoiding sharing socks, towels, or shoes with others
How is athlete’s foot treated?
Athlete’s foot can usually be cured with topical antifungal creams, gels, sprays, or powders, several of which are available over-the-counter (OTC). These products should be used twice daily until the rash has resolved (usually two to four weeks) and then used weekly in order to prevent recurrence of the infection. If you suspect you have athlete’s foot, but find that it does not improve as expected with one of the following medications, it is important to see a doctor to confirm the diagnosis and obtain appropriate treatment.
The following topical medicines are effective for athlete’s foot:
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Certain types of athlete’s foot may be more difficult to treat, including the moccasin and inflammatory types. In cases that do not respond to topical antifungal preparations, oral antifungal tablets or capsules are required. Physicians prescribe a particular medication and dose based on the patient’s age, weight, and any other medical conditions they may have.
The following oral medicines are effective for athlete’s foot:
- Terbinafine 250 mg daily for two to six weeks
- Itraconazole 200 – 400 mg daily for two to four weeks
- Fluconazole 150 mg weekly for up to four weeks
- Griseofulvin microsize five to seven milligrams per kilogram of body weight (up to 500 mg) daily for six to twelve weeks
Adjunctive treatment with drying powders, drying agents, and creams that soften the thick layers of skin on the feet can also be helpful:
- Drying powders: these contain talc or cornstarch and may contain an antifungal medicine as well. They are used daily on the feet and in the shoes to keep the feet dry and kill fungus.
- Keratolytic agents: Urea 10% or 20% cream and ammonium lactate 12% cream are potent moisturizers that help remove thick layers of dead skin on the soles of the feet, allowing the antifungal medicines to penetrate better and kill the fungus faster.
- Aluminum acetate (Domeboro or Burow’s solution): in cases of inflammatory (blistering) athlete’s foot, the feet can be soaked once or twice daily for five minutes in a solution made by dissolving aluminum acetate in water at a dilution of 1:10-1:40. This will help dry up the blister fluid and speed healing.
- Aluminum chloride 12% or 20%: this anti-perspirant solution may be applied to the feet at bedtime for several weeks in order to decrease daytime sweating and help keep the feet dry. Decreased sweating may reduce the risk of recurrence of athlete’s foot.
Is athlete’s foot a serious condition?
Since the fungi that cause athlete’s foot live on keratin protein found in the outer layer of the skin, the hair, and the nails, they cannot invade deeper tissues and cause serious illness. Nonetheless, athlete’s foot can be very uncomfortable and unsightly, prompting affected individuals to seek medical treatment. Since athlete’s foot is very common and quite contagious, it is important to treat from a public health perspective.
It is especially important to treat athlete’s foot in people who have diabetes or are immunosuppressed, because they run an increased risk of developing a secondary bacterial infection from the open cracked skin of athlete’s foot. Another reason for treating athlete’s foot is that fungus growing on the feet can spread to other parts of the body, causing jock itch, ringworm, or fungal toenails, which may be harder to treat than the original athlete’s foot.
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