Athlete's Foot

Athlete's foot, known medically as tinea pedis, is a common fungal infection of the feet. It is primarily caused by dermatophytes, including Trichophyton rubrum, T. mentagrophytes, and Epidermophyton floccosum. This infection can affect any part of the foot but is most commonly found between the toes or on the soles.

Signs and Symptoms

Athlete's foot manifests in several forms: chronic interdigital, plantar (moccasin foot), acute ulcerative, and vesiculobullous. The interdigital type is most common, presenting between the toes, typically between the fourth and fifth digits. Symptoms range from asymptomatic to itching, redness, and ulceration, with potential maceration of the skin.

Plantar athlete's foot, often caused by T. rubrum, produces erythematous plaques covered by hyperkeratotic scales on the foot's sole. Vesiculobullous athlete's foot, usually caused by T. mentagrophytes, is characterised by sudden outbreaks of itchy blisters on an erythematous base, commonly complicated by secondary bacterial infections.

Complications

Untreated athlete's foot may lead to cracked skin, bacterial infections, and inflammation of the lymphatic vessels. The condition can spread to the toenails, resulting in onychomycosis, and to other body parts, potentially causing tinea corporis or tinea cruris. Severe itching can lead to excoriations, facilitating further spread of the fungus and secondary infections.

Causes

Athlete's foot is caused by dermatophytes, which thrive in warm, moist environments. These funguses digest keratin in dead skin layers. T. rubrum is the most common cause among the general population, while T. mentagrophytes is more prevalent in athletes.

Transmission

The condition is highly contagious, spreading through direct contact or indirectly via contaminated surfaces like bathroom floors, towels, and shared footwear. Pets can also be carriers, transferring the fungus through petting.

Risk Factors

Risk factors include previous infections, adulthood, male gender, diabetes, weakened immune systems, and hyperhidrosis. HIV/AIDS also increases susceptibility due to compromised immune function.

Diagnosis

Diagnosis is primarily clinical, based on visual inspection and symptoms like itching and scaling. When uncertain, direct microscopy of a potassium hydroxide preparation of a skin scraping (KOH test) can confirm the diagnosis by revealing multiple septate branching hyphae. A Wood's lamp is typically not useful for diagnosing athlete's foot.

Prevention

Preventive measures include keeping feet dry, clipping toenails short, changing socks frequently, and wearing sandals in communal areas. Using antifungal powders and cleaning contaminated surfaces with chlorine bleach can prevent recurrence and spread. Avoiding the sharing of footwear and towels is also very important.

Treatment

Athlete's foot often resolves without medication in 30-40% of cases. However, topical antifungal treatments, such as terbinafine, clotrimazole, and miconazole, are more effective. Treatment typically continues until all layers of the skin are replaced, which takes 2 to 6 weeks.

Topical Treatments

Effective topical antifungals include miconazole nitrate, clotrimazole, tolnaftate, terbinafine, and butenafine. Plantar-type athlete's foot may require keratolytic and humectant medications to improve antifungal penetration. Topical glucocorticoids may be prescribed to alleviate inflammation and itching.

Oral Treatments

For severe or refractory cases, oral antifungals like terbinafine, fluconazole, or itraconazole are effective. These medications are particularly useful when the infection affects the nails or other body parts.

Epidemiology

Athlete's foot affects about 15% of the global population, with 70% experiencing it at some point. It is more prevalent in those who wear occlusive footwear and those engaged in occupations or activities like mining, soldiering, and athletics. The disease has been described as a "penalty of civilisation" due to its association with modern footwear and communal spaces.

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Self-assessment MCQs (single best answer)

What is the medical term for athlete's foot?

Which of the following fungi is a common cause of athlete's foot?

Which type of athlete's foot is characterised by erythematous plaques covered by hyperkeratotic scales?

Which of the following is NOT a typical sign or symptom of athlete's foot?

How is athlete's foot primarily diagnosed?

Which of the following is a risk factor for athlete's foot?

What is the most effective way to prevent the spread of athlete's foot in communal areas?

Which topical antifungal treatment is commonly used for athlete's foot?

What is the name of the diagnostic test that uses potassium hydroxide to confirm athlete's foot?

Which of the following occupations is associated with a higher risk of athlete's foot?