What is the first-line treatment for an adult patient with tinea corporis, a fungal infection of the skin?

Treatment of Tinea Corporis

For adult patients with tinea corporis, topical antifungal therapy with azoles (clotrimazole, miconazole) or allylamines (terbinafine) applied once or twice daily for 2-4 weeks is first-line treatment for localized disease. 1, 2, 3

When to Use Topical vs. Oral Therapy

Topical antifungals are appropriate for:

• Localized, limited skin involvement 2, 3
• Immunocompetent patients 3, 4
• First-line treatment in most cases 1, 4

Oral antifungals are indicated when:

• The infection is extensive or covers a large body surface area 2, 3, 5
• Topical therapy has failed 1, 3
• Hair follicle involvement is present 3
• The patient is immunocompromised 3, 5, 6
• The infection is recurrent despite adequate topical treatment 1, 7

Specific Topical Treatment Regimens

For mild to moderate tinea corporis:

• Terbinafine 1% cream or gel applied once daily for 1-2 weeks 2
• Clotrimazole cream applied twice daily for 2-4 weeks 8, 4
• Miconazole cream applied twice daily for 2-4 weeks 8, 4
• Continue treatment for at least one week after clinical clearing 4

Oral Antifungal Options for Extensive Disease

When oral therapy is required:

• Terbinafine 250 mg daily for 1-2 weeks is particularly effective against Trichophyton species (the most common cause of tinea corporis) 1, 2
• Itraconazole 100 mg daily for 15 days achieves an 87% mycological cure rate and is effective against both Trichophyton and Microsporum species 1, 2

Terbinafine is generally preferred over itraconazole because it has fewer drug interactions, making it safer in patients taking multiple medications 6. However, itraconazole is contraindicated in heart failure and has significant interactions with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin 2.

Critical Diagnostic Considerations

Before initiating treatment, consider mycological confirmation:

• Obtain potassium hydroxide (KOH) preparation from skin scrapings using scalpel scraping 1, 3, 5
• Culture on Sabouraud agar if diagnosis is uncertain or treatment fails 1, 5, 7
• Clinical diagnosis alone is unreliable—tinea corporis can be confused with eczema, psoriasis, or other dermatoses 3, 5

However, you can start empiric topical treatment immediately for typical presentations while awaiting culture results, as topical therapy is low-risk 4. Reserve diagnostic testing for atypical presentations, treatment failures, or when considering oral therapy 3, 5.

Treatment Monitoring and Endpoints

The definitive endpoint is mycological cure, not just clinical improvement 1, 2. This is a critical pitfall—lesions may appear clinically resolved while fungal elements persist, leading to rapid recurrence 1.

• Continue treatment for at least one week after clinical clearing 4
• If using oral therapy, repeat mycology sampling at the end of treatment and monthly until clearance is documented 1, 2
• Baseline liver function tests are recommended before initiating terbinafine or itraconazole, especially with pre-existing hepatic abnormalities 8, 2

Prevention of Recurrence

Essential preventive measures include:

• Avoid skin-to-skin contact with infected individuals 1, 2
• Do not share towels, clothing, or personal items 1, 5
• Cover lesions during treatment 1
• Screen and treat family members, especially for anthropophilic species like Trichophyton tonsurans (over 50% of family members may be affected) 1, 2
• Clean contaminated combs, brushes, and fomites with disinfectant or 2% sodium hypochlorite solution 1, 2
• Keep skin dry and cool 5
• Wear protective footwear in public facilities to prevent concurrent tinea pedis 2

Common Pitfalls to Avoid

Never use combination antifungal-corticosteroid products as first-line therapy 3. While they may provide faster symptomatic relief due to anti-inflammatory properties, they can cause skin atrophy, mask the infection, and potentially worsen the condition (tinea incognito) 3, 4.

Do not stop treatment based on clinical appearance alone—this is the most common cause of treatment failure and recurrence 1, 4.

Avoid empiric oral therapy without knowing the causative organism when possible, as terbinafine has poor efficacy against Microsporum species 9. If oral therapy is needed urgently, itraconazole covers both genera 1, 2.

Emerging Resistant Infections

Be aware that emerging tinea infections may be more severe and generally do not improve with first-line topical or oral antifungals 3. These infections may require prolonged oral antifungal therapy and specialized diagnostic testing including susceptibility testing 3. If a patient fails standard therapy, consider referral to dermatology and obtain fungal culture with susceptibility testing 3.