Tinea (dermatophytosis) treatment protocol

1. Confirm diagnosis before systemic therapy

• Examine the active scaly edge of a lesion.
• Do KOH microscopy where feasible. Send fungal culture/speciation and susceptibility testing if disease is extensive, recurrent, atypical, or does not respond to adequate therapy.
• For nail disease, confirm fungus by KOH, PAS stain, culture, or PCR before oral therapy.
• Consider alternatives: eczema, psoriasis, candidal intertrigo, pityriasis rosea, erythrasma, and contact dermatitis.

2. Localized tinea corporis, cruris, or limited pedis

First-line: topical antifungal

Adjunctive measures

• Keep folds and toe webs dry.
• Loose cotton clothing for cruris/corporis.
• Change socks daily; dry footwear, avoid sharing shoes/towels.
• Treat coexisting tinea pedis and onychomycosis, which can perpetuate recurrent cruris/corporis.
• Look for affected household contacts or pets when recurrent infection suggests a continuing source.

3. When to use oral treatment

• Extensive or multiple-site tinea corporis/cruris
• Failure after a correctly applied topical course
• Hair follicle involvement, Majocchi granuloma, or deep inflammatory disease
• Severe/moccasin-type or recurrent tinea pedis
• Tinea capitis, beard involvement, or onychomycosis
• Immunocompromise
• Suspected terbinafine-resistant dermatophyte infection

Common adult oral regimens

• Check baseline liver history and generally obtain liver function testing when starting oral terbinafine or itraconazole, particularly with prolonged treatment or liver risk.
• Review drug interactions, especially with itraconazole.
• Avoid systemic azoles or terbinafine in pregnancy unless a specialist judges that benefit outweighs risk.
• Do not use oral ketoconazole for dermatophytosis because of hepatotoxicity and interaction risk.
• Nystatin does not treat dermatophyte tinea.

4. Site-specific protocol

A. Tinea corporis and tinea cruris

1. KOH from active border if uncertain, recurrent, or widespread.
2. Localized: topical terbinafine or azole.
3. Reassess after 2-3 weeks.
4. If no improvement:
   • Check adherence and whether a topical steroid or steroid-antifungal combination has been used.
   • Reconsider diagnosis.
   • Culture/speciate, especially for extensive disease.
   • Use oral treatment if confirmed and appropriate.

B. Tinea pedis

1. Treat interdigital disease with topical antifungal and meticulous drying.
2. Hyperkeratotic/moccasin form: topical antifungal plus keratolytic such as urea or salicylic acid may improve penetration.
3. Severe, widespread, recurrent, or treatment-resistant disease: confirm and consider oral therapy.
4. Treat any infected nails simultaneously to reduce recurrence.

C. Tinea capitis

• Always systemic antifungal therapy. Topical treatment alone does not reach the infected hair shaft.
• Obtain KOH/culture before therapy where possible.
• Antifungal shampoo such as ketoconazole or selenium sulfide 2-3 times weekly can reduce spore shedding but is adjunctive only.
• Examine close contacts and avoid sharing combs, caps, pillows, and hair accessories.
• Kerion needs prompt dermatology assessment because delayed treatment can result in scarring alopecia.

D. Tinea unguium / onychomycosis

• Confirm mycologically before oral therapy.
• Oral terbinafine is usually preferred for dermatophyte nail infection.
• Debride thick nail and treat coexistent tinea pedis.
• Clinical cure takes months because normal nail must grow out, even after mycological eradication.

5. Avoid common errors

• Do not prescribe fixed-dose antifungal-corticosteroid combinations routinely, such as clotrimazole-betamethasone.
• Do not use potent topical steroids on an unconfirmed “fungal rash.” They can suppress inflammation, alter morphology, promote spread, and cause tinea incognito.
• Do not stop topical treatment immediately when redness settles.
• Do not call every hypopigmented/scaly trunk rash “tinea.” Pityriasis versicolor is not dermatophyte tinea and has a different regimen.

6. Resistant or recalcitrant tinea