What is the cause of peeling and itching on the feet and toes, and how can it be treated, considering a possible history of skin conditions like eczema or psoriasis?

Peeling and Itching of Feet and Toes

The most likely diagnosis is tinea pedis (athlete's foot), and you should treat with topical terbinafine 1% cream applied twice daily for 1-2 weeks, which cures most cases and relieves itching, burning, cracking, and scaling. 1, 2

Diagnostic Approach

Confirm the diagnosis before treating by obtaining a KOH preparation or fungal culture from skin scrapings of the affected areas, as clinical diagnosis alone has low accuracy. 3, 4 Look specifically for:

• Light-colored scaling and peeling on the soles and margins of the feet, which characterizes squamous hyperkeratotic tinea pedis 3
• Interdigital involvement with fissuring, scaling, or maceration between toes—this serves as a portal for secondary bacterial infection 3
• Dystrophic toenails, which commonly coexist with chronic tinea pedis 3
• Absence of inflammatory signs (erythema, warmth, tenderness, pain) to rule out cellulitis or other inflammatory conditions 3

The causative organisms are predominantly Trichophyton rubrum and T. mentagrophytes. 1, 3

First-Line Treatment

For interdigital tinea pedis (between the toes):

• Apply terbinafine 1% cream twice daily for 1 week 1, 2
• This is more effective than longer courses of other antifungal agents 1

For plantar involvement (bottom or sides of foot):

• Apply terbinafine 1% cream twice daily for 2 weeks 1, 3, 2
• Wash affected skin with soap and water and dry completely before applying 2

Alternative topical options if terbinafine is unavailable:

• Ciclopirox olamine 0.77% cream/gel achieves approximately 60% clinical and mycological cure at end of treatment, and 85% two weeks after treatment 1
• Clotrimazole 1% cream is less effective but widely available over-the-counter 1

When to Use Oral Therapy

Reserve oral antifungals for:

• Severe disease 1
• Failed topical therapy 1
• Concomitant onychomycosis 1
• Immunocompromised patients 1
• Extensive involvement 3

Oral terbinafine 250 mg once daily for 1-2 weeks is the most effective systemic treatment, with fungicidal action allowing shorter treatment duration. 1, 3 It has similar efficacy to 4 weeks of topical clotrimazole but with faster clinical resolution. 1

Alternative oral options:

• Itraconazole 100 mg daily for 2 weeks has similar mycological efficacy but may have slightly higher relapse rates 1
• Fluconazole is less effective than both terbinafine and itraconazole for dermatophyte infections 1

Adjunctive Measures to Enhance Treatment

• Apply urea 10% cream three times daily to reduce hyperkeratosis and improve penetration of antifungal agents 3
• Ensure complete drying of feet after bathing, particularly between toes 3
• Wear well-fitting, ventilated shoes and change shoes and socks at least once daily 2

Prevention of Recurrence

Critical prevention strategies:

• Apply foot powder after bathing, which reduces tinea pedis rates from 8.5% to 2.1% 1, 3
• Change socks daily and wear cotton, absorbent socks 1
• Thoroughly dry between toes after showering 1
• Clean athletic footwear periodically 1
• Wear protective footwear in public bathing facilities, gyms, and hotel rooms 1

Address contaminated footwear:

• Discard old, moldy footwear when possible 1
• Place naphthalene mothballs in shoes and seal in a plastic bag for minimum 3 days 1
• Apply antifungal powders containing miconazole, clotrimazole, or tolnaftate inside shoes 1
• Spray terbinafine solution into shoes periodically 1

Prevent household transmission:

• Treat all infected family members simultaneously to prevent reinfection 1
• Avoid sharing toenail clippers with family members 1
• Cover active foot lesions with socks before wearing underwear to prevent spread to groin 1

Special Considerations for Eczema or Psoriasis History

If the patient has a history of eczema or psoriasis, distinguish these conditions from tinea pedis:

• Psoriasis of palms/soles presents with well-demarcated erythematous plaques with silvery scale, often symmetric, and follows a chronic stable course rather than acute onset over weeks 5
• Eczema typically shows more inflammation, vesiculation, and weeping compared to the dry scaling of tinea pedis 4
• KOH preparation is essential to differentiate fungal infection from inflammatory dermatoses 3, 4

Important caveat: TNF-alpha antagonists used for psoriasis can paradoxically induce pustular psoriasis of the palms and soles in patients without prior psoriasis history. 5

Common Pitfalls to Avoid

• Failing to obtain mycological confirmation leads to misdiagnosis and inappropriate treatment 3, 4
• Neglecting to address contaminated footwear causes reinfection 1
• Not treating all infected family members simultaneously results in reinfection 1
• Stopping treatment too early before completing the full course leads to treatment failure 2
• Ignoring concomitant toenail involvement, which occurs in up to one-third of cases and serves as a reservoir for reinfection 6