Onychomycosis, commonly known as toenail fungus, is a prevalent infection caused primarily by dermatophytes, yeasts, or non-dermatophytic molds. It typically begins as a white or yellow spot beneath the tip of the toenail, progressing to cause discoloration, thickening, and brittleness. A common concern for individuals using nail cosmetics is whether the polish can harbor these infectious agents or contribute to their spread. This article explores the survival of fungi within the polish bottle and the risks associated with applying polish over an existing infection.
Survival of Fungus in Polish Bottles
The contents of a typical nail polish bottle are not conducive to active fungal growth due to their chemical composition. Nail polish is mostly made up of highly volatile organic solvents, such as butyl acetate and ethyl acetate, which constitute approximately 70% to 80% of the formula. These solvents are toxic to most microorganisms, and the lack of water and nutrients prevents fungi from metabolizing and multiplying.
While active growth is inhibited, dormant fungal spores remain a possibility. Spores, the hardy reproductive units of fungi, can be introduced into the bottle via the brush after contact with an infected nail. Studies suggest that certain components, particularly in some top coats containing mineral or soy oil, may allow spores of common pathogens like Trichophyton rubrum to maintain viability for up to 60 days.
Most pigmented polishes and base coats contain potent chemical components like toluene, formaldehyde, and xylene that inhibit fungal organisms. The primary danger posed by the bottle is not fungal growth in the polish, but the risk of the applicator brush acting as a fomite. When a brush transfers spores from an infected nail back into the bottle, it creates a vehicle for indirect transmission to healthy nails.
Risk of Applying Polish Over Infected Nails
The most significant risk occurs when polish is applied to a nail already infected with onychomycosis. Fungi, especially dermatophytes, thrive in environments that are warm, dark, and moist. Applying a layer of cosmetic polish, particularly thick, occlusive kinds like gel polish, seals the nail plate and creates a microclimate suited for fungal proliferation.
The polish acts as a barrier that traps moisture on or around the nail bed. This sealing prevents the natural evaporation of water, leading to chronic hydration beneath the lacquer, which accelerates the fungal life cycle. The opaque nature of the polish also blocks light, creating the darkness fungi prefer for optimal colonization.
This sealed environment can lead to distal onycholysis, where the nail plate separates from the underlying nail bed, creating a larger space for fungal debris. Covering the infection also masks visual symptoms, delaying diagnosis and the start of appropriate antifungal treatment. If a person uses a topical antifungal medication, the non-porous layer of cosmetic polish physically blocks the drug from penetrating the nail to reach the infection site.
Increased fungal activity and delayed treatment can cause the infection to become more severe, resulting in thicker, more disfigured nails that are harder to treat. In advanced cases, the infection can spread to the surrounding skin, potentially leading to a secondary condition like athlete’s foot. Polish does not cause the infection, but it actively contributes to worsening the condition by creating ideal growth conditions.
Preventing Transmission and Cross-Contamination
Maintaining strict hygiene practices is the most effective way to prevent the spread of toenail fungus through cosmetic application. Avoid sharing nail polish, especially with anyone who has a visible nail infection. Keeping personal polish bottles ensures the brush has only contacted your own nails, minimizing the risk of introducing foreign spores.
Proper sterilization of all manicure and pedicure tools is paramount in preventing transmission. Instruments like nail clippers, files, and cuticle pushers can harbor and transfer fungal spores and keratin debris. Metal tools should be thoroughly cleaned and sterilized with an appropriate disinfectant or an autoclave between uses.
When visiting a professional nail salon, vigilance is necessary to ensure proper sanitation protocols are followed. Clients should confirm that all instruments are sterilized in a medical-grade autoclave or that disposable tools are used. It is advisable to bring your own file, buffer, and polish to eliminate the risk of cross-contamination from shared salon products.
Foot Care Habits
Simple foot care habits can reduce the overall risk of infection. Ensuring that feet and the spaces between the toes are completely dry after bathing or swimming helps remove the moisture fungi require. Allowing toenails to remain polish-free for a few days between applications also permits air exposure, discouraging a favorable fungal environment.