Athlete's foot

Summary

• Athlete's foot is an umbrella term describing common fungal infections of the feet.
• Athlete's foot refers to a dermatophyte infection of the spaces between the toes, usually between the fourth and fifth toes, but not limited to that space.
• Although it is most often described as the infection between the toes, it may also affect the sole of the foot, the whole foot, and the nails.
• It may occur in association with other fungal skin infections, such as fungal infection of the toenails, feet or groin.
• The condition usually responds to self-care, provided that care is applied for long enough.
• If the infection persists, long-term medication and preventive measures may be needed.

Alternative names

tinea pedis; ringworm of the foot

Definition

Athlete's foot is an extremely common skin disorder and is the most common and most persistent of the fungal (tinea) infections.

It affects most people at some point in their lives, and unless treated correctly and effectively, it can become persistent, and or recurrent.

Athlete’s foot is caused by one of three different groups of organism, Dermatophytes, yeasts and moulds. Of these, Dermatophytes are by far and away the most common. Yeasts are usually secondary invaders, and moulds extremely rare.

Widespread yeast Infections can occur in immune suppressed patients

The dermatophytes that cause athlete's foot and similar infections, called tinea infections, live on the dead tissues of the hair, nails, and outer skin layers.

Athlete's foot may occur in association with other fungal skin infections such as jock itch. Jock itch is a dermatophyte infection of the groin area. It occurs most frequently in adults. Often Jock itch is secondary, as people scratch the foot, then the groin causing the infection to spread.

Athlete’s foot spreads rapidly in moist shared environments, like public change rooms, sports clubs change rooms and showers. In fact, any public area where people walk barefoot can be an area where athlete’s foot is spread.

Causes

The body normally hosts a variety of microorganisms, including bacteria, dermatophytes, and yeast-like fungi (such as Candida). Some of these are useful to the body. Others may, under proper conditions, multiply rapidly and cause infections.

The fungi that cause athlete's foot thrive in warm, moist areas. Susceptibility to this infection is increased by poor hygiene, occlusive footwear (closed-up shoes, such as tennis shoes), prolonged moist skin and minor skin or nail injuries. Fungi reproduce by creating spores (seeds, for want of a better description), and these spores can stay dormant in shoes, socks, bath mats and floors and, even if the surface is cleaned, they can remain viable and infect people at a later stage.

Tinea infections are contagious and can be passed through direct contact, or contact with items such as shoes, stockings, and shower or pool surfaces (because of the spores). They also can be transmitted from contact with pets that carry the fungus. Athlete's foot may be brief or long-term and may recur even after treatment.

Symptoms

Athlete’s foot has three typical presentations:

• interdigital athlete’s foot: this appears as moist, pink, white flaking skin between the toes with a reddened area in the splits in the skin. This is usually very itchy. There is a bacterial condition that looks similar, but does not itch. So the appearance of this presentation with the itch is usually athlete’s foot
• vesiculo-pustular presentation: this presents as small blisters, usually in the arch area under the foot. The blisters have a small red halo, with a grey blister and a dark peak to the blister. They are very itchy, and burst easily when scratched. The itch soon abates when the blister is burst, but this just spreads the infection and causes more blisters to appear. Soon there will be a large area that will be peeling, with new blisters forming.
• the dry scaly type: this appears as dry skin over the surface of the foot, and often it covers the entire foot. This is called a moccasin infection as it resembles the shape of a moccasin. The edges of the dry skin are slightly reddened with small flakes of skin around the edges of the infected areas. This is often not symptomatic at all and patients will just treat it with moisturizing creams, thinking it is dry skin.

Nail Infections

The nail plate becomes discoloured with a yellowish gold straw to yellow brown discolouration under the nail plate. The nail can retain its normal thickness, or it can thicken and become distorted. It can appear as a few wedge-shaped streaks in the nail plate from the nail edge backwards to larger areas up to, and including, the entire nail plate. It can appear on one nail, or up to, and including, all ten nails. This is asymptomatic, unless the infection has caused the nail to distort, thicken or become ingrown. 

Athlete's foot may be symptomless or itching and burning may be present. On examination, the affected area appears red and scaly. The scaling is often whitish, due to maceration of the skin, caused by the moist environment.

Tinea infection may also involve the nails and the rest of the foot. These lesions are red and scaly, or vesiculopustular and crusted.

The nails may be discoloured, thickened and crumbly.

Diagnosis

The diagnosis is usually clinical, and based primarily on the appearance of the skin. However, laboratory tests can be used to confirm a diagnosis in one of the following ways. Lab tests can be beneficial when deciding on which medication is best suited.

• Skin or nail scrapings are sent for fungal culture (fungi from flecks of skin or nail are allowed to grow on special material).
• Skin lesion biopsy (examination may show dermatophyte).
• Skin lesion KOH exam (skin or nail scrapings in potassium hydroxide show dermatophytes when examined under a microscope).

Treatment

Most people will self-medicate and athlete's foot will often respond to self-care.

There are many over-the-counter preparations from pharmacies that are effective in treating athlete’s foot. However people often do not treat the condition for long enough and ignore re-infection from shoes and socks. This can lead to recurrence, and re-infection.

In severe, widespread, or chronic infections the advice of a Podiatrist, GP or Dermatologist will be beneficial in treating the condition correctly. Scrapings may be taken, oral medication may be provided and, most importantly, patient education on preventing recurrence will be given.

Tinea pedis (skin infections) and onychomycosis (nail infections) in a diabetic person, must only be treated under supervision of a doctor of podiatrist. And it must be treated as quickly as possible.

Keep the skin clean and dry. Wash thoroughly with soap and water and dry the area carefully and completely. Blow-drying the feet with a hair dryer removes excess water from the outer layers of skin and is more effective than drying with a towel. Wear clean socks and change socks and shoes as often as necessary to keep the feet dry. Topical, over-the-counter antifungal powders or creams, such as those that contain miconazole or clotrimazole, may be used to control the infection.

Severe or chronic infection may require further treatment by the health care provider. Oral antifungal medications may be given. Other topical antifungal medications, such as ketoconazole or terbinafine, may be needed. Antibiotics may be needed to treat secondary bacterial infections.

Wet dressings or medicated soaks are used to clean raw, wet or weeping lesions. Dry, scaly lesions may respond to topical creams or lotions.

Prognosis

Athlete's foot infections range from mild to severe. They may persist or recur, but they generally respond to treatment. Long-term medication and preventive measures may be needed. The prognosis is good, provided the infection is treated for long enough (usually 7-10 days after all symptoms have cleared). Shoes are treated with anti-fungal powders, or cleaned or replaced in severe cases. Socks are washed at a very high temperature, or replaced, and shared surfaces scrubbed with JIK (one part JIK to three parts water) and rinsed very well.

Complications

• Recurrence of athlete's foot
• Secondary bacterial skin infections such as impetigo, ecthyma and cellulitis
• Lymphangitis, lymphadenitis
• Systemic side effects of medications (see specific medication)
• Do not use cortisone as a treatment, unless prescribed by a healthcare provider.

When to call your doctor

Call for an appointment with your healthcare provider if athlete's foot symptoms do not respond to self-care measures.

Prevention

Good personal hygiene helps prevent and treat athlete's foot. Antifungal or drying powders may be used as a preventive measure if a person is susceptible to athlete's foot, or if exposed frequently to areas where athlete's foot fungus is suspected (public showers, etc.).

Wearing sandals at a public shower or pool may help prevent athlete's foot, but these measures have not been shown to be of definite benefit. Drying the feet thoroughly after bathing or swimming has been shown to be the best means to prevent the disorder.

Woollen socks allow moisture to be drawn away from the feet. Change the socks as frequently as needed to keep feet dry and, at least, on a daily basis. Shoes should be well ventilated and preferably made from organic material, such as leather. It may be helpful to alternate shoes daily, so each pair can dry completely between wearings.

Information supplied by the National Institutes of Health.

Reviewed by Prof H.F. Jordaan, MBChB, Mmed (Derm).

Revised by Sean J Pincus, Podiatrist NHDPod(SA) BSc Hons (Brighton), September 2010.

South African Podiatry Association (SAPA)