Is onychomycosis contagious, how is it transmitted, and what are the recommended treatments?

Is Fungal Nail Infection Contagious?

Yes, onychomycosis is contagious and can spread to other family members through direct contact with infected skin scales and nail debris that contain infectious fungal spores. 1

Mechanism of Transmission

The infection spreads through arthroconidia (arthrospores), which are the infectious fungal forms shed from infected nails and skin. 1 These spores are particularly effective at spreading infection because they:

• Require no external nutrition to survive 1
• Resist adverse environmental conditions 1
• Are produced in large numbers through fragmentation of fungal hyphae 1
• Remain viable in exfoliated skin scales and nail debris 1

Direct contact with contaminated material—such as shared nail clippers, towels, shoes, or walking barefoot on contaminated surfaces—facilitates person-to-person transmission. 1

Clinical Significance of Contagiousness

Infected nails serve as a reservoir of fungi with potential for spread to the patient's own feet, hands, and groin, as well as to other household members if left untreated. 1 The British Association of Dermatologists explicitly states that fungal diseases are contagious and may spread to other family members. 1

Experimental studies have confirmed that all morphological forms of dermatophytes (macroconidia, microconidia, arthrospores, and infected skin scales) can cause human infection when applied to nail tissue. 1

Treatment Rationale Based on Contagiousness

Treatment is medically indicated—not merely cosmetic—because untreated onychomycosis poses ongoing transmission risk and can lead to serious complications, particularly in diabetic patients (foot ulcers, osteomyelitis, cellulitis, gangrene). 1

First-Line Systemic Treatment

• Oral terbinafine 250 mg daily for 12 weeks (toenails) or 6 weeks (fingernails) is the first-line treatment, achieving 70-80% cure rates for toenails and 80-90% for fingernails. 2
• Baseline liver function tests and complete blood count are required before initiating therapy. 2

Second-Line Options

• Itraconazole 200 mg daily for 12 weeks continuously, or pulse therapy at 400 mg daily for 1 week per month (3 pulses for toenails, 2 for fingernails) is recommended for patients intolerant of terbinafine. 2
• Itraconazole must be taken with food and acidic beverages for optimal absorption. 2
• Fluconazole 150-450 mg once weekly for at least 6 months is a third-line option with fewer drug interactions. 2

Topical Therapy (Mild Cases Only)

• Amorolfine 5% lacquer applied once or twice weekly for 6-12 months achieves approximately 50% clinical cure rates. 3
• Efinaconazole 10% solution applied daily for 48 weeks shows mycological cure rates approaching 50%. 3

Prevention of Transmission

To prevent spread to family members and reinfection, patients must implement comprehensive environmental decontamination measures: 2, 4

• Discard or decontaminate contaminated footwear by placing naphthalene mothballs in shoes sealed in plastic bags for minimum 3 days 2
• Apply antifungal powders inside shoes regularly 2, 4
• Avoid sharing nail clippers, towels, or footwear 4
• Wear protective footwear in public bathing facilities, gyms, and hotel rooms 4
• Wear cotton absorbent socks and change daily 4
• Keep nails trimmed short 4
• Treat all infected family members simultaneously to prevent reinfection cycles 3

Common Pitfalls

The misconception that onychomycosis is merely cosmetic leads to undertreatment and continued transmission. 1 Approximately 50% of patients experience pain or discomfort, 30% have difficulty wearing footwear, and the infection significantly impacts quality of life through emotional embarrassment and work-related difficulties. 1

Even with optimal treatment, recurrence rates reach 40-70%, making prevention strategies essential. 3 The 48-72 week follow-up period from treatment initiation is necessary to detect relapse. 2