Tinea Pedis (Athlete’s Foot)
BASICS
DESCRIPTION
- Most common dermatophyte infection
- Contagious, especially in communal environments
- Frequently associated with:
- Tinea manuum
- Tinea cruris
- Tinea unguium
- Clinical forms:
- Interdigital (most common)
- Hyperkeratotic (moccasin type)
- Vesiculobullous type
EPIDEMIOLOGY
- Age: 20–50 years (can occur at any age)
- Gender: ♂ > ♀ (4:1)
- Prevalence:
- ~4–10% active at any given time
-
70% will experience it during lifetime
Pediatric Considerations
- Rare in young children
- More common post-puberty
Geriatric Considerations
- More common due to:
- Reduced immunity
- Poor distal perfusion
ETIOLOGY & PATHOPHYSIOLOGY
- Dermatophytes infect only nonviable keratinized tissue
- Common organisms:
- Trichophyton rubrum (chronic)
- Trichophyton interdigitale (acute)
- Trichophyton tonsurans
- Epidermophyton floccosum
- No known genetic pattern
RISK FACTORS
- Hot, humid environments
- Excessive sweating
- Occlusive footwear
- Immunosuppression
- Chronic topical steroid use
PREVENTION
- Personal hygiene
- Use of sandals in shared wet areas
- Dry feet thoroughly, especially between toes
- Frequent sock changes
- Antiperspirants or drying powders
- Antifungal shoe sprays or powders
COMMON ASSOCIATIONS
- Onychomycosis
- Tinea cruris
- Tinea manuum
- Hyperhidrosis
DIAGNOSIS
HISTORY
- Pruritic, scaling rash on foot, typically interdigital
- May involve:
- Soles, dorsum, sides of feet
- Strong odor, maceration, ulceration
- Secondary bacterial infection or dermatophytid reaction possible
PHYSICAL EXAM
- Acute: scaling, redness, white maceration between toes
- Chronic (moccasin type): erythema, scaling of soles and sides of feet
- May be bilateral or unilateral
DIFFERENTIAL DIAGNOSIS
- Interdigital:
- Erythrasma
- Impetigo
- Candidal intertrigo
- Pitted keratolysis
- Moccasin type:
- Psoriasis
- Contact dermatitis
- Chronic eczema
- Vesiculobullous:
- Dyshidrotic eczema
- Bullous impetigo
- Autoimmune blistering diseases
DIAGNOSTIC TESTS
- KOH microscopy: branching hyphae
- Fungal culture (Sabouraud agar) if unclear diagnosis
- PCR: for resistant/recurrent cases
- Wood’s lamp: Not helpful for T. rubrum
TREATMENT
TOPICAL ANTIFUNGALS – First-Line for Local Disease
| Agent | Dose/Frequency | Duration |
|---|---|---|
| Terbinafine 1% | BID | Until 3 days after rash clears |
| Econazole 1% | BID | 2–4 weeks |
| Ketoconazole 2% | BID | 2–4 weeks |
| Tolnaftate 1% | BID | 2–4 weeks |
| Aluminum acetate soaks | 20 min BID | For vesiculobullous type |
| Aluminum chloride 30% | BID | For hyperhidrosis |
Continue topical antifungals for at least 3 days beyond clinical resolution.
SYSTEMIC ANTIFUNGALS – For Severe, Extensive, or Nail Involvement
| Drug | Dose | Notes |
|---|---|---|
| Itraconazole | 200 mg BID × 7 days | >90% cure |
| Fluconazole | 150 mg weekly × 4 weeks | Alternative |
| Terbinafine | 250 mg/day × 2–6 weeks | Also for onychomycosis |
| Griseofulvin | 250–500 mg/day × 3 weeks | Second-line; monitor LFTs |
⚠ Monitor LFTs with systemic therapy
⚠ Itraconazole: avoid in CHF, use with acidic drinks if on PPIs
⚠ Griseofulvin: avoid in porphyria, SLE, or liver disease
PEDIATRIC DOSING
| Drug | Weight-based dosing |
|---|---|
| Griseofulvin | 10–15 mg/kg/day |
| Terbinafine | <20 kg: 62.5 mg/day 20–40 kg: 125 mg/day >40 kg: 250 mg/day |
| Itraconazole | 3–5 mg/kg/day |
| Fluconazole | 6 mg/kg/week |
ADJUNCTIVE & ALTERNATIVE THERAPIES
- Baking soda soaks (½ cup/quart water)
- White vinegar soaks (1:1 vinegar:water) – for bacterial coinfection
- Eczematoid changes: topical corticosteroids
- Secondary bacterial infections: topical/systemic antibiotics
REFERRAL
- Dermatology referral if:
- Extensive/refractory disease
- Immunocompromised host
- Diagnosis in doubt
ONGOING CARE & FOLLOW-UP
- Monitor for recurrence
- Educate on:
- Hygiene
- Footwear habits
- Sock-changing frequency
- Prevent tinea cruris by:
- Wearing socks before underwear
- Treating all affected sites simultaneously
PROGNOSIS
- Often chronic or recurrent
- Requires long-term prevention strategies
- Recurrences common in hot, humid climates
COMPLICATIONS
- Secondary bacterial infection: risk of cellulitis, lymphangitis
- Dermatophytid reaction (id reaction)
- Chronic hyperkeratosis
- Spread to nails (onychomycosis)
ICD-10 CODE
- B35.3 – Tinea Pedis
CLINICAL PEARLS
- Treat for 4 weeks minimum
- Dry feet well, especially between toes
- Dusting powders help prevent recurrence
- Consider fungal infection in recalcitrant eczema of the foot
- Always check for concomitant onychomycosis or tinea cruris