This cure is based on a scientific study with good results (DOI: 10.7547/87507315-89-3-124) and made into DIY home remedy.
The study used a solution of 0.1% Benzalkonium chloride which is a common ingredient in non-alcohol based hand sanitizer. At 0.1% there is no risk of skin irritation unless you are allergic.
The other ingredient was allantoin which is a mild keratolytic and surfactant. This can be replaced with a crushed up aspirin (acetylsalicylic acid), dissolved in approximately 100ml of solution. Mild body soap may also be added in a small amount however this isn't necessary but it may help.
The study applied the treatment to the infected nail and the base of the nail twice daily over 10 months.
• Benzalkonium chloride 0.1% (Non-alcohol based hand sanitizer or a concentrate diluted appropriately)
• 1 crushed aspirin, dissolved in 100ml of solution (optional, dilute further or omit if you experience a skin reaction)
• A small amount of gentle soap or bodywash (optional, omit if you experience a skin reaction)
Cut away all excess infected nail with separate nail scissors or clippers so that you don't spread the infection to other nails.
Using a separate file, file back the nail on all surfaces well often. Ideally this should be repeated at least twice a week or more for best results.
Apply solution to infected nails once in the morning and once in the evening, ensuring that you cover underneath the nail where possible and where the base of the nail joins your finger or toe. Ensure that you apply the solution after showering and drying yourself for best results.
Continue until the infected nail has been removed and only uninfected nail remains.
This is a safe method of long-term treatment of nail fungus which has good results in controlled study environments.
Hand sanitizer can be applied regularly to the skin and left to dry and has very low risk of causing irritation.
I have personally been applying this solution regularly for about a month and a half and I can see a clear diagonal line of new, uninfected nail emerging from the base of my infected toe. I have often applied the solution more often than twice a day with no ill effects.
If you are a busy person or you have a disability which makes this sort of treatment regime difficult you can try applying the solution to a cotton ball or similar and attaching this to your infected nail using tape or a band-aid. The benefit of this is that you can re-wet the bandage for reapplication of the treatment, and as the solution remains in contact with the infected nail for a longer period this should result in a higher success rate. Ensure that you pay close attention to ensure that you are not causing irritation with the prolonged skin contact from this method.