Athlete's foot

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[3]

• Athlete’s foot (tinea pedis) is a fungal infection of the skin that causes scaling, flaking, and itching of affected areas.
• It mainly affects the soles, skin over toes, interdigital spaces and nails. ^[1]
• It is typically transmitted in moist areas where people walk barefoot, such as showers or bathhouses.
• Athlete’s foot is caused infection with a dermatophyte fungus.
• Although the condition typically affects the feet, it can spread to other areas of the body, including the groin.
• Athlete’s foot can be prevented by good hygiene, and is treated by a number of pharmaceutical and other treatments.

• The Oxford English Dictionary documents written usage of the term in 1928 (1928 Lit. Digest 22 December. 16/1), which seems to undercut the claim by W. F. Young, Inc. that the term “athlete’s foot” was originated, rather than simply popularized, as part of an advertising campaign for Absorbine Jr. during the 1930s.^[2]
• Athlete’s foot gained popularity during the World Wars due to a very high percentage of soldiers wearing occlusive footwear and using common baths, etc.

• Athlete’s foot is caused by a parasitic fungus and is a communicable disease.^[3]
• It is typically transmitted in moist environments where people walk barefoot, such as showers, bath houses, and locker rooms.^[4][5][3]

• It can also be transmitted by sharing footwear with an infected person, or less commonly, by sharing towels, socks, footwear or clothes with an infected person.

• Athlete’s foot can usually be diagnosed by visual inspection of the skin. Affected skin appears flaky and macerated and rash is usually diffuse and patchy affecting more than 1 toe and sole of the foot.
• Where the diagnosis is in doubt direct microscopy of a potassium hydroxide preparation (known as a KOH test) may help rule out other possible causes, such as eczema or psoriasis.^[6]
• A KOH preparation is performed on skin scrapings from the affected area.
• The KOH preparation has an excellent positive predictive value, but occasionally false negative results may be obtained, especially if treatment with an anti-fungal medication has already begun.

• A Wood’s lamp, although useful in diagnosing fungal infections of the hair (Tinea capitis), is not usually helpful in diagnosing tinea pedis since the common dermatophytes that cause this disease do not fluoresce under ultraviolet light.
• However, it can be useful for determining if the disease is due to a non-fungal afflictor.

• There are many conventional medications (over-the-counter and prescription) as well as alternative treatments for fungal skin infections, including athlete’s foot.

• Important with any treatment plan is the practice of good hygiene.
• Several placebo controlled studies report that good foot hygiene alone can cure athlete’s foot even without medication in 30-40% of the cases.^[7] However, placebo-controlled trials of allylamines and azoles for athlete’s foot consistently produce much higher percentages of cure than placebo.^[8]

• The fungi that cause athlete’s foot can live on shower floors, wet towels, and footwear.
• Athlete’s foot is caused by a fungus and can spread from person to person from shared contact with showers, towels, etc.
• Hygiene therefore plays an important role in managing an athlete’s foot infection.
• Since fungi thrive in moist environments, it is very important to keep feet and footwear as dry as possible.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]

• The Oxford English Dictionary documents written usage of the term in 1928, which seems to undercut the claim by W. F. Young, Inc. that the term “athlete’s foot” was originated, rather than simply popularized, as part of an advertising campaign for Absorbine Jr. during the 1930s.^[1]
• Athlete’s foot was first reported in 1908 by Sabouraud and Arthur Whitfield.
• Tinea pedis became more popular in the US and United Kingdom because of the popularisation of occlusive footwear and the habit of wearing socks which retained moisture around the feet.^[2]

• Tinea affecting other areas than scalp, was first seen in soldiers fighting in the trenches during WW1.
• Prior to this, tinea affecting the feet was very rare.
• Tinea pedis interestingly affected members of the British Army who bathed more often and maintained general personal hygiene. Softening of the skin due to repeated washing and wearing socks/stockings under many layers of clothes provided a cozy environment for tinea to flourish. ^[3]
• A study published about the incidence of tinea pedis among the American troops during WW1 showed that 13% of all ranks in the US Navy were affected, and the numbers were even higher among those men who were recruited from college. ^[4]
• This was seen as a major issue because even though it is not a deadly condition, the affected could not change clothes in the middle of combat or difficult operations.
• The number of people infected only increased during WW2, with it being rampant among the troops stationed in the tropics.
• Paul de Kruif wrote an article in the Readers Digest (De Kruif, P. , ‘A working cure for athlete’s foot’, Reader’s Digest, 1942, 40: 46–48.) advocating for the use of a mixture of camphor and phenol to treat athlete’s foot. But in some cases this combination lead to death due to exposure.
• Tinea infections were so high in the British troops stationed in South-East Asian countries that they set up a research unit. It was reported that 79.5% of the soldiers in SE Asia had tinea pedis. ^[5]

• The first therapy for tinea pedis was developed by H. Raistrick by isolating it from Penicillium gresiofulvum.^[6]
• Research found that griseofulvin inhibited fungal cell wall formation and cell division. ^[7]
• Ketoconazole was discovered by a Belgian company in 1977^[8]. Ketoconazole was approved for clinical use in 1982.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[3]

• Athlete’s foot is caused by a parasitic fungus and is a communicable disease.^[1]

• It is typically transmitted in moist environments where people walk barefoot, such as showers, bath houses, and locker rooms.^[2][3][1]
• It can also be transmitted by sharing footwear with an infected person, or less commonly, by sharing towels with an infected person.

• The various parasitic fungi that cause athlete’s foot can also cause skin infections on other areas of the body, most often under toenails (onychomycosis) or on the groin (tinea cruris).
• It is transmitted even by sharing footwear.

• Majority of the cases of athlete’s foot are caused by Trichophyton rubrum. But other organisms such as Epidermophyton floccosum, Trichophyton interdigitale, Trichophyton mentagrophytes are also implicated in development of tinea pedis.
• Trichophyton tonsurans has been identified as a cause of tinea pedis infections in children. ^[4]
• The fungi cause breakdown of superficial skin through secretion of enzymes called keratinases which dissolve keratin.^[5]
• The fungal cell wall of dermatophytes also contain mannans which diminish the body’s inflammatory response by decreasing antigen presenting and processing.^[6]
• It is interesting to note that Trichophyton rubrum often causes chronic and long drawn infection due to increased production of mannans which decrease the turnover and proliferation of keratinocytes.^[7]
• The dermatophytes thrive in a moist and damp environment. Maceration, superficial tears in the skin and chronic occlusive footwear usage for long periods of time increase the chance of getting infected.
• Several innate factors such as transferrin, beta globulins and sebum have a growth-inhibitory effect on these fungi. Transferrin, particularly the unsaturated form inhibits growth by binding iron which is required for growth and propagation of dermatophytes. ^[8]
• A poor immune system such as in immunocompromised individuals also is a predilection for infection with tinea spp.^[9]

Scrapings of skin affected with tinea pedis prepared with KOH show the following features.

• Hyperkeratosis
• Acanthosis
• Perivascular infiltrate

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]

• Trichophyton rubrum – most common cause of athlete’s foot.
• Trichophyton interdigitale
• Trichophyton tonsurans
• Trichophyton mentagrophytes
• Epidermophyton floccosum

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]

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• Psoriasis, pustular psoriasis^[1]
• Cutaneous Candidiasis
• Allergic contact dermatitis
• Keratoderma
• Maceration of interdigital space by infection or friction
• Erythrasma^[2]
• Dyshidrosis

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• The prevalence of athlete’s foot is estimated to be around 10% worldwide. ^[1]
• Males are more likely to be infected than females.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]

The fungus thrives in warm, moist areas. Risk for getting athlete’s foot increases if for any reason, the feet are moist or damp for a long time. Common risk factors are listed below.

• Wearing closed toe shoes, especially if they are plastic-lined.
• Keeping feet wet for prolonged periods of time
• Sweating a lot
• Developing a minor skin or nail injury
• Humid environment
• Swimming in communal swimming pools.

All the above contribute to increased risk of getting infected with athlete’s foot. ^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sanjana Nethagani, M.B.B.S.[2]

• Tinea pedis usually presents as a chronic infection due to its mild symptoms.

• Since the infection is limited to the stratum corneum, it is easy to treat with topical medication^[1].

• However, chronic cases may require systemic therapy.

• Long standing tinea pedis infections cause maceration, scaling and breaks/tears in the skin barrier which allow bacterial infection to seep in.
• Bacterial skin infections such as the following are common

1. Cellulitis
2. Lymphangitis
3. Lymphadenitis

• Complications are usually seen in patients who are immobile (stroke/ hemiplegia), diabetes, chronic edema of the feet and immunocompromised patients.
• Rarely, even fungal osteomyelitis can result from a long standing infection, coupled with other risk factors such as immunosuppression or immobility.^[2]

• Dermatophytid reaction (also called identity or id reaction) is a dermatological complication of a fungal infection, like tinea pedis, wherein, an infection of the feet or toes produces an allergic skin reaction on another part of the body which is unaffected, such as the fingers.
• This is not as a result of touching the infected area.
• The cause is postulated to be circulating antibodies to the fungal antigens or cytotoxic T cells which affected an unrelated patch of skin away from the site of primary infection.^[3]

• Athlete’s foot infections range from mild to severe and may last a short or long time.
• Generally, underlying conditions such as immunodeficiency etc dictate the prognosis of tinea pedis infection.
• Prognosis is usually good in healthy people with no underlying conditions and they only require a short course of topical anti fungal creams.
• They may persist or recur, but they generally respond well to treatment.
• Long-term medication and preventive measures may be needed in some cases

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