What is the recommended treatment for a fungal rash on the leg?

Treatment for Fungal Rash on Leg

For a fungal rash on the leg (tinea corporis/cruris), topical terbinafine 1% cream applied once or twice daily for 1 week is the most effective first-line treatment, achieving mycological cure rates exceeding 90%. 1, 2

Topical Therapy (First-Line)

Terbinafine 1% cream is superior to other topical agents:

• Apply once or twice daily for 1 week only 1, 2
• Achieves mycological cure in >80-93% of patients 3, 1
• Fungicidal mechanism provides sustained effect after treatment cessation 3, 2
• More effective than clotrimazole 1% cream used for 4 weeks (93.5% vs 73.1% cure rate) 1
• Superior to miconazole, bifonazole, and oxiconazole formulations 3

Alternative topical azoles (if terbinafine unavailable):

• Clotrimazole 1% cream applied twice daily for 4 weeks 1
• Miconazole 2% cream applied twice daily for 2-4 weeks 3
• These are fungistatic (not fungicidal), requiring longer treatment duration and having higher recurrence rates 2

Oral Therapy (When Topical Fails or Extensive Disease)

Reserve systemic treatment for:

• Extensive or chronic involvement 4
• Failed topical therapy 5
• Areas where topical application is impractical 4

Oral treatment options (in order of preference):

1. Terbinafine 250 mg daily for 1-2 weeks 3, 5

   • Most effective oral agent for dermatophyte infections 3
   • Achieves >80% mycological cure 3
   • Fungicidal with residual tissue effect 3

2. Itraconazole 100 mg daily for 2 weeks OR 200 mg daily for 7 days 5

   • Effective alternative to terbinafine 5
   • Comparable efficacy for tinea corporis/cruris 5

3. Fluconazole 50-100 mg daily for 2-3 weeks OR 150 mg once weekly for 2-3 weeks 5

   • Less effective than terbinafine for dermatophyte infections 6
   • Better activity against Candida than dermatophytes 6
   • Consider if Candida infection suspected 7

Critical Pitfalls to Avoid

• Do not use terbinafine if Candida infection suspected - it has limited activity against yeasts; use azoles instead 3, 2
• Do not stop fungicidal topicals early - even though 1 week is sufficient, patients often discontinue when skin appears healed, which is appropriate with terbinafine but leads to recurrence with fungistatic agents 2
• Do not use fluconazole as first-line for dermatophytes - it is inferior to terbinafine for these infections 6
• Monitor liver function if using oral fluconazole - rare but serious hepatotoxicity can occur, though no clear dose-relationship exists 7

Treatment Algorithm

1. Confirm dermatophyte infection (vs. Candida) based on location and appearance
2. Start topical terbinafine 1% cream once-twice daily for 1 week 1, 2
3. If extensive/chronic or topical fails: Switch to oral terbinafine 250 mg daily for 1-2 weeks 3, 5
4. If Candida suspected: Use topical or oral azole (clotrimazole, miconazole, or fluconazole) instead 8, 2