What is the cause of a white skin lesion between the toes that is pruritic and sometimes painful?

White Skin Lesion Between Toes: Tinea Pedis (Athlete's Foot)

The white, itchy, and sometimes painful skin lesion between your toes is most likely tinea pedis (athlete's foot), specifically the interdigital type, caused by dermatophyte fungi—predominantly Trichophyton rubrum or Trichophyton mentagrophytes. 1

Clinical Presentation

The interdigital form of tinea pedis characteristically presents as:

• Fine scaling, maceration, and fissuring between the toes, most commonly affecting the lateral toe clefts 1
• White, macerated appearance of the skin in the toe web spaces 2
• Pruritus (itching) as a prominent symptom 1
• Pain, particularly when fissures develop in the affected areas 1, 2

This is the most common presentation of foot fungal infections, affecting up to 22% of swimmers and runners 1.

Causative Organisms

The infection is caused by dermatophyte fungi that thrive in warm, humid environments 1:

• Trichophyton rubrum (most common) 2
• Trichophyton mentagrophytes (also called T. interdigitale) 1, 2
• Less commonly, Epidermophyton floccosum 1

Risk Factors

Your infection risk increases with 1:

• Warm, humid environments (swimming pools, communal showers, gyms)
• Occlusive footwear that retains moisture
• Hyperhidrosis (excessive sweating)
• Male gender (more common in men than women) 1
• Obesity and diabetes (additional risk factors) 1
• Direct contact with contaminated surfaces or infected individuals 2

Diagnosis Confirmation

While clinical diagnosis has low accuracy, potassium hydroxide (KOH) wet-mount examination of skin scrapings from the active border is recommended as point-of-care testing 2. This can be confirmed by fungal culture if necessary 2.

Treatment Approach

For Localized Interdigital Infection

Topical antifungal therapy applied once to twice daily for 1-6 weeks is the mainstay of treatment 2:

First-line topical agents (all highly effective):

• Allylamines (e.g., terbinafine): RR of treatment failure 0.33 (95% CI 0.24-0.44) compared to placebo 3, 4
• Azoles (e.g., clotrimazole, ketoconazole): RR 0.30 (95% CI 0.20-0.45) 3
• Ciclopiroxolamine cream 0.77%: Applied twice daily for 4 weeks, achieving ~60% cure rate 1

Allylamines cure slightly more infections than azoles (RR 0.63,95% CI 0.42-0.94) and offer once-daily dosing 3.

When Oral Therapy Is Needed

Reserve systemic treatment for 2:

• Severe or extensive disease
• Failed topical therapy
• Concomitant nail involvement (onychomycosis)
• Immunocompromised patients

Oral terbinafine 250 mg once daily for 1 week has similar efficacy to 4 weeks of topical clotrimazole but with faster clinical resolution 1, 5.

Prevention Strategies

To prevent recurrence and spread 1:

• Thoroughly dry between toes after showers or bathing
• Change socks daily and use absorbent cotton socks
• Apply foot powder after bathing (reduces rates from 8.5% to 2.1%) 1
• Wear protective footwear in communal areas (pools, gyms, locker rooms)
• Periodically clean athletic footwear or discard old shoes
• Avoid sharing towels and personal items 1
• Consider applying antifungal powder in shoes 1

Important Caveats

• Untreated tinea pedis can spread to nails, creating a reservoir for reinfection 1, 2
• Family members should be examined and treated simultaneously to prevent transmission 1
• Recurrence rates can be high (40-70%) without proper preventive measures 1
• In diabetic patients, untreated infection can lead to bacterial superinfection, cellulitis, or foot ulcers 1

The prognosis is excellent with appropriate antifungal treatment, but adherence to preventive measures is essential to avoid recurrence 2.