Topical treatment of nail diseases is hampered by the nail plate barrier, consisting of dense cross-linked keratin fibres held together by cysteine-rich proteins and disulphide bonds, which prevents penetration of antifungal agents to the focus of fungal infection. Acidified nitrite is an effective treatment for tinea pedis. It releases nitric oxide (NO) and other NO-related species. NO can react with thiol (-SH) groups to form nitrosothiols (-SNO).
Finnen, M. J., Hennessy, A., McLean, S., Bisset, Y., Mitchell, R., Megson, I. L., & Weller, R. (2007). Topical application of acidified nitrite to the nail renders it antifungal and causes nitrosation of cysteine groups in the nail plate. The British Journal of Dermatology, 157(3), 494-500. https://doi.org/10.1111/j.1365-2133.2007.08063.x