To use Listerine mouth wash as a treatment for toenail fungus, soak the affected feet in Listerine for about 30 minutes at a time, once or twice per day. Listerine is likely safe for topical use, however its effectiveness against toenail fungus has not been evaluated by the FDA as of 2015, notes HealthGuidance.org.
When using Listerine as an anti-fungal foot soak, allow the affected nail to soak in the mouthwash for 30 minutes, then scrub the nail gently. Rinse and dry the feet thoroughly after soaking. Top10HomeRemedies.com recommends soaking the affected foot once or twice per day until the fungus clears. Fungal infections of the nail may take several months to clear, notes HealthGuidance.
Active ingredients in Listerine include the essential oils eucalyptol, menthol, thymol and methyl salicaylate. Eucalytpol has some anti-fungal properties, while thymol and menthol work as antiseptic agents, according to Listerine.com.
The anti-fungal properties of eucalyptus have not been evaluated by the FDA, and more research is needed to confirm the effectiveness of eucalyptus in most of its uses, according to WebMD. Though eucalyptus may be unsafe when used in its undiluted form, when diluted in Listerine it is unlikely to cause irritation. Users who experience irritation after repeated Listerine soaks should discontinue use for a period of time.