Tinea Pedis

Introduction

Tinea pedis, commonly known as athlete’s foot, is a fungal infection of the skin on the feet. It is one of the most common superficial fungal infections and can affect people of all ages, though it is more prevalent among athletes, those who wear tight-fitting shoes, and individuals with sweaty feet. The condition can be uncomfortable and is often recurrent.

Aetiology

Tinea pedis is primarily caused by dermatophyte fungi, most commonly Trichophyton rubrum and Trichophyton interdigitale. The infection is typically acquired through direct contact with contaminated surfaces or objects, such as floors, towels, or shoes. Factors that promote the development of tinea pedis include:

• Warm, Moist Environments: The fungi thrive in warm, damp environments such as public showers, locker rooms, and swimming pools.
• Occlusive Footwear: Wearing tight, non-breathable shoes can create a moist environment conducive to fungal growth.
• Hyperhidrosis: Excessive sweating of the feet can increase the risk of developing tinea pedis.
• Compromised Skin Barrier: Minor skin injuries, such as cuts or abrasions, can provide an entry point for the fungi.
• Immunosuppression: Individuals with weakened immune systems are at higher risk of developing fungal infections, including tinea pedis.

Clinical Presentation

Tinea pedis can present in several forms, with symptoms varying depending on the type of infection:

• Interdigital Type:
  • This is the most common form, characterised by scaling, maceration, and fissuring of the skin between the toes, particularly between the fourth and fifth toes.
  • It may be associated with itching, burning, and a malodorous discharge.
• Moccasin Type:
  • This form presents with dry, scaly, and thickened skin on the soles and sides of the feet, resembling the pattern of a moccasin.
  • The skin may become hyperkeratotic and fissured, causing discomfort and sometimes pain.
• Vesiculobullous Type:
  • This less common form presents with the sudden appearance of vesicles or bullae (blisters) on the sole or dorsum of the foot.
  • The blisters may be itchy or painful and can become secondarily infected if ruptured.

Diagnosis

The diagnosis of tinea pedis is often clinical, based on the characteristic appearance of the affected areas. Additional tests may be used to confirm the diagnosis or rule out other conditions:

• Fungal Culture: A sample of skin scrapings can be cultured to identify the specific dermatophyte species causing the infection. This is particularly useful in recurrent or resistant cases.
• Wood’s Lamp Examination: Although less commonly used for tinea pedis, a Wood’s lamp can help differentiate tinea pedis from other conditions such as erythrasma, which fluoresces coral-red under UV light.

Management

Tinea pedis can be effectively treated with topical or systemic antifungal medications, depending on the severity and extent of the infection:

Topical Treatments

• Topical Antifungals: Over-the-counter antifungal creams, gels, or sprays such as terbinafine, clotrimazole, or miconazole are effective for most cases of tinea pedis. These should be applied to the affected areas and surrounding skin for at least two weeks, continuing for a few days after symptoms resolve to prevent recurrence.

Systemic Treatments

• Oral Antifungals: In severe, widespread, or recalcitrant cases, oral antifungal medications such as terbinafine or itraconazole may be prescribed. Treatment duration is typically 2-6 weeks, depending on the severity of the infection.

Adjunctive Measures

• Foot Hygiene: Encourage regular washing and thorough drying of the feet, particularly between the toes, to reduce moisture and prevent fungal growth.
• Footwear: Advise patients to wear breathable, moisture-wicking socks and well-ventilated shoes. Avoiding tight, occlusive footwear can help reduce recurrence.
• Antifungal Powders or Sprays: These can be used in shoes and on feet to keep them dry and prevent reinfection.

Prevention

To prevent the development or recurrence of tinea pedis, consider the following strategies:

• Good Foot Hygiene: Regularly wash feet with soap and water, and ensure they are completely dry, especially between the toes.
• Footwear Choice: Wear breathable shoes and change socks daily. Avoid wearing the same pair of shoes every day to allow them to dry out fully.
• Use of Antifungal Powders: Applying antifungal powder to feet and inside shoes can help keep feet dry and prevent fungal growth.
• Avoid Walking Barefoot in Public Areas: Use protective footwear, such as flip-flops, in communal showers, locker rooms, and around swimming pools.

When to Refer

Referral to a dermatologist may be necessary in the following situations:

• Refractory Cases: If tinea pedis does not respond to standard treatment, referral for further evaluation and management is recommended.
• Complicated Infections: If there is evidence of secondary bacterial infection, severe inflammation, or the development of cellulitis, specialist input may be required.
• Extensive Disease: Widespread or severe infections, particularly those involving the nails (onychomycosis) or large areas of the foot, may benefit from specialist management.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Fungal Skin Infections. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Fungal Infections: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng75 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Systemic Antifungal Agents. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).