How do I diagnose and treat tinea cruris?

Diagnosis and Treatment of Tinea Cruris

Terbinafine 1% cream applied once daily for 1 week is the first-line treatment for tinea cruris, with high efficacy and FDA approval for children 12 years and older. 1

Diagnosis

• Diagnosis is based on clinical appearance plus direct microscopy of a potassium hydroxide (KOH) preparation of skin scrapings 2
• Culture or histologic examination is rarely required for diagnosis but can be helpful in resistant cases 2
• Key clinical features include:
  • Erythematous, sharply demarcated lesions with raised, scaly borders in the groin area 3
  • May extend to the inner thighs and buttocks but typically spares the scrotum 3
  • Pruritus is a common symptom 2

First-Line Topical Treatment

• Terbinafine 1% cream applied once daily for 1 week is recommended by the American Academy of Pediatrics 1
• Advantages of terbinafine include:
  • Fungicidal action (rather than fungistatic) 4
  • Shorter treatment duration compared to azoles 4
  • High efficacy against Trichophyton species, which commonly cause tinea cruris 5

Alternative Topical Treatments

• Butenafine applied twice daily for 2 weeks is an effective over-the-counter alternative for adults 1
• Clotrimazole 1% cream applied twice daily for 2-4 weeks is another effective option 6, 4
• Other azole antifungals (econazole, ketoconazole, miconazole, oxiconazole) applied twice daily for 2-4 weeks are also effective 4
• Naftifine 1% has demonstrated superior efficacy compared to placebo (NNT = 3) 6

When to Consider Oral Therapy

• Oral antifungal therapy is indicated when: 7, 8
  • The infection is resistant to topical treatment
  • The infected areas are large or widespread
  • Lesions are macerated with secondary infection
  • Infection involves complex skin folds of external genitalia
  • Patient is immunocompromised

Oral Treatment Options

• Itraconazole 100 mg daily for 15 days (87% mycological cure rate) 7
• Terbinafine 250 mg daily for 1-2 weeks (particularly effective against T. tonsurans) 7
• A combination of topical and oral antifungal drugs can shorten the treatment period and improve patient adherence 8

Treatment Duration and Follow-up

• Topical treatment should continue for at least one week after clinical clearing of infection 2
• Follow-up should include both clinical and mycological assessment 7
• Treatment failure may require extending treatment duration or switching to an alternative agent 7

Prevention Strategies

• Cover active foot lesions with socks before wearing undershorts to reduce direct contamination 1
• Completely dry the groin area after bathing 1
• Use separate towels for drying the groin and other parts of the body 1
• Avoid sharing towels, clothing, or other personal items 3
• Keep the skin dry and cool at all times 3
• Practice good personal hygiene 3

Special Considerations

• In cases with significant inflammation, a short course of a combination antifungal/steroid agent may be beneficial, but should be used with caution due to potential for causing atrophy 2
• For interdigital tinea pedis with erosion or contact dermatitis, begin with a combination of topical corticosteroid therapy and oral antifungal drugs 8