Calling Dr. Google: A Closer Look At The Myths And Realities Of Apple Cider Vinegar For Onychomycosis

I am sure each week in your practice you have a patient discuss a home remedy he or she found on Google that is supposed to clear onychomycosis. Like me, you can name a litany of the possibly logical and illogical “cures” displayed with a simple Google search. When faced with patients who have tried these home remedies and have not seen the result they wanted, I do not want to judge or make light of what they have used, but certainly want to give them the facts as to why common household remedies have or have not worked. 

Let us focus on apple cider vinegar, which has been touted as a cure-all tonic for many different ailments with websites dedicated to its properties. It is generally inexpensive and easy to obtain. Our patients are bombarded with faceless, picture-less “my toenails look better!” testimonials that claim the anonymous person’s nail disease was cured.

What is in apple cider vinegar? It contains maleic acid, acetic acid, pectin, beta-carotene, acetoin, methanol, alanine, ethanol, ethyl acetate, lactic acid, methanol, glycerol and tartaric acid in addition to mineral salts, phosphorus, potassium, chloride, sodium and other minerals.^1,2 It is the maleic acid that purportedly has both bactericidal and fungicidal properties. Some have theorized that acetate can inhibit lanosterol demethylase, which means it would impact ergosterol production in a fungal cell.³ Others have felt that acetic acid is permeable to the cell membrane and the presence of it is toxic to the cell.⁴

Have there been any clinical trials showing that apple cider vinegar creates a mycological or clinical cure for onychomycosis? No. 

The closest study I found to dissect apple cider vinegar’s antifungal properties was in the Journal of Prosthodontics.¹ The authors studied apple cider vinegar for denture stomatitis, which is usually caused by Candida albicans. This study showed the minimum inhibitory concentration (MIC) of apple cider vinegar versus nystatin, the common antifungal for Candida, but more importantly, the study showed the microbial death curve. The microbial death curve is more of a dynamic measure as it allows “quantitative analysis of the fungicidal activity and of the time required until microbial death,” ultimately showing the behavior of the antifungal agent in the presence of the organism.

In this study, the kinetics of antifungal activity of apple cider vinegar varied at all concentrations and time intervals from nystatin and control.¹ All groups (apple cider vinegar and nystatin) showed fungistatic activity, with testing at MIC and MICx2, between 0 and 180 minutes. When testing at MICx4, the researchers found that apple cider vinegar only exhibited fungistatic activity between 0 and 30 minutes. However, after 30 minutes, apple cider vinegar began to exhibit fungicidal activity. Ultimately, for Candida albicans, apple cider vinegar concentration and time exposed to the organism will affect whether it acts as a fungistatic agent or a fungicidal agent. 

How do we translate this to our practice? At this point, we do not have MIC data or microbial death curves on apple cider vinegar’s effect on T. rubrum or T. mentagrophytes, the most common dermatophytes we see with toenail onychomycosis. Although it seems that apple cider vinegar does exhibit antifungal behavior in vitro, we cannot make that direct connection in vivo to onychomycosis or determine the concentration/time exposed needed to have a fungicidal effect. More studies are needed to determine what, if any, true effect apple cider vinegar can have on fungal toenails. At this stage, it remains a folk remedy with widely varying results. 

References

1. Mota AC, de Castro RD, de Araujo Oliveira J, de OIiveira Lima E. Antifungal activity of apple cider vinegar on Candida species involved in denture stomatitis. J Prosthodont. 2015;24(4):296-302
2. Heikefelt C. Chemical and sensory analyses of juice, cider and vinegar produced from different apple cultivars. Alnarp, Swedish University of Agricultural Sciences, Faculty of Landscape Planning, Horticulture and Agricultural Sciences, Department of Plant Breeding and Biotechnology, 2011. Available at https://stud.epsilon.slu.se/2481/1/heikefelt_c_110415.pdf .
3. Arneborg N, Jespersen L, Jakobsen M. Individual cells of Saccharomyces cerevisiae and Zygosaccharomyces bailii exhibit different short-term intracellular pH responses to acetic acid. Arch Microbiol. 2000;174(1-2):125-128.
4. Guldfeldt L, Arneborg U. Measurement of the effects of acetic acid and extracellular pH on intracellular pH of nonfermenting, individual Saccharomyces cerevisiae cells by fluorescence microscopy. Appl Environ Microbiol. 1998;64(2):530-534