Do ultraviolet (UV) light shoe inserts effectively kill fungus in shoes?

UV Light Shoe Inserts for Fungal Decontamination

UV light shoe sanitizers can effectively reduce fungal contamination in footwear and may serve as a useful adjunct measure to prevent reinfection in patients with onychomycosis and tinea pedis.

Evidence for Efficacy

Laboratory studies demonstrate that UVC shoe sanitizers significantly reduce dermatophyte colonization in footwear. A controlled study using an infected shoe model showed that commercial UVC sanitizing devices effectively reduced fungal burden in both leather and athletic shoes contaminated with Trichophyton rubrum and Trichophyton mentagrophytes, the most common causative organisms of nail and foot fungal infections 1. The reduction in fungal colonization was achieved with just one cycle of irradiation, with no additional benefit from multiple cycles 1.

Mechanism and Antimicrobial Activity

• UVC light (200-290 nm wavelength) demonstrates direct antimicrobial activity against dermatophytes through DNA damage 2
• UVB light shows superior antifungal efficacy compared to UVA, with the highest antimicrobial activity at 300 nm wavelength 2
• In vitro studies show that fungal organisms are highly susceptible to UV irradiation, with some species achieving total growth inhibition at appropriate doses 2

Clinical Context and Reinfection Risk

Footwear serves as a significant reservoir for reinfection in patients with superficial fungal infections. The British Journal of Dermatology guidelines emphasize that contaminated shoes contribute to the high recurrence rates (40-70%) seen with onychomycosis 3. This is particularly problematic because:

• Trichophyton rubrum is commonly found in hotel bedrooms, carpeting, gyms, and public bathing facilities 3
• Recurrence rates for treated onychomycosis range from 10-53% due to persistent fungal reservoirs 4
• The nail plate lacks adaptive immune response, making reinfection from environmental sources more likely 4

Recommended Preventive Strategy

The British Journal of Dermatology recommends shoe decontamination as part of a comprehensive prevention strategy:

• Discard old contaminated footwear when possible, or decontaminate shoes with naphthalene mothballs 5
• Apply antifungal powders inside shoes regularly 5
• Consider spraying terbinafine solution into shoes periodically 5
• UV shoe sanitizers can be incorporated as an additional decontamination method based on demonstrated efficacy 1, 4

Practical Considerations

Modern UV sanitization methods show promise but require proper application:

• UV irradiation represents a more practical approach than older methods (formaldehyde fumigation, boiling) that can damage shoe integrity or cause health complications 4
• Scraping the inner shoe surface is more effective than swabbing for assessing fungal burden, suggesting that UV light must penetrate surface irregularities 1
• Combining UV sanitization with other preventive measures (antifungal powders, proper foot hygiene, cotton socks) enhances protection against reinfection 5, 4

Limitations and Caveats

• Most evidence comes from laboratory studies rather than clinical trials demonstrating reduced reinfection rates in actual patients 1, 4
• Standardized parameters for optimal UV exposure duration and intensity have not been fully established 4
• UV sanitization should be viewed as an adjunct to, not a replacement for, appropriate systemic or topical antifungal therapy 3, 5
• Cost considerations may limit accessibility for some patients 4

UV shoe inserts represent a scientifically sound adjunctive measure that addresses the footwear reservoir contributing to fungal reinfection, though they should be combined with appropriate medical treatment and other preventive strategies for optimal outcomes.