Athlete’s foot is a common fungal infection of the skin that affects the feet. It is caused by a group of fungi called dermatophytes, which thrive in specific environmental conditions. After successful treatment, the primary concern is preventing recurrence, as shoes worn during the infection become a reservoir of fungal spores, posing a significant re-infection risk.
Understanding the Fungal Threat
Dermatophytes are filamentous fungi that feed on keratin, the protein found in skin, hair, and nails. These fungi survive and multiply in conditions that mimic the environment inside a sweaty shoe: dark, warm, and moist.
Shoes, especially closed-toe and athletic footwear, create a humid microclimate perfect for fungal growth. The fungi rely on shed skin cells and sweat trapped within the materials for nutrients and moisture. Because fungal spores can persist long after symptoms clear, consistent sanitation of footwear is necessary to break the cycle of re-infection.
Determining Survival Time in Shoes
The survival time of the fungus in shoes depends heavily on the internal environment. Dermatophyte spores are resilient and can remain dormant for days, weeks, or even months, waiting for favorable conditions. Moisture is the primary factor driving survival, as the fungus requires a damp environment to become active and multiply.
Shoe material also plays a significant role in fungal retention. Synthetic materials hold moisture longer than canvas or leather, sustaining the fungus. Even if a shoe feels dry, microscopic spores can survive for several weeks in a dormant state. Temperature is another variable; while typical room temperatures allow spores to remain viable, extreme heat is lethal, making thermal methods effective for eradication.
Practical Steps for Shoe Sanitization
Eradicating fungal spores requires a consistent, multi-faceted approach, as surface cleaning is insufficient. The goal is to kill the fungus deep within the shoe’s lining and materials. It is recommended to alternate between pairs of shoes, allowing each pair to dry thoroughly for 24 to 48 hours between wears, which significantly reduces moisture.
Chemical Treatments
Chemical treatments involve using antifungal sprays or powders specifically designed for footwear. Products containing fungicidal agents should be sprayed or dusted liberally inside the shoe, especially on the insoles. Allow the product to sit for the time specified on the label to ensure full penetration.
Heat Treatment
Heat treatment is highly effective, as dermatophytes are killed at high temperatures. A minimum of 140 degrees Fahrenheit (60 degrees Celsius) is necessary to eliminate spores. Specialized shoe dryers can achieve this heat without damaging the material, or heat-tolerant shoes can be washed at 60 degrees Celsius.
UV Light Sanitizers
For a non-chemical option, ultraviolet (UV) light sanitizers made for shoes destroy the fungus’s DNA. These devices are placed inside the shoe for a set period and can kill up to 99.9% of microbes.
For ongoing maintenance, removing the insoles for separate, thorough drying and dusting the inside of the shoe with a zinc oxide-containing powder can help control moisture and reduce the fungal load. Combining these methods offers the best chance of fully sterilizing footwear and stopping the cycle of re-infection.