The Antifungal Activity of Apple Cider Vinegar Against Dermatophytes and Its Effects on Human Keratinocytes

Background: Dermatophytes are a widespread fungal infection with growing concerns of antifungal resistance. Apple Cider Vinegar (ACV) is a traditional remedy known for its antimicrobial properties, but its efficacy against specific dermatophytes and its safety on host cells are not yet well-characterised. Methods: In this study, the in vitro antifungal activity of ACV was evaluated against six clinically relevant dermatophyte species by measuring the Minimum Inhibitory Concentration (MIC). The lytic mechanism was investigated by measuring the release of intracellular components. Additionally, the effects of ACV on human keratinocytes (HaCaT) were evaluated by measuring mitochondrial membrane potential (ΔΨm) and lipid peroxidation. Results: ACV exhibited potent antifungal activity, with MICs ranging from 1.56% to 3.12% for five of six strains. ACV induced fungal cell lysis in a concentration-dependent manner. In HaCaT cells, 10% ACV induced significant mitochondrial depolarisation and increased oxidative stress. In contrast, 1% ACV induced potential mitochondrial hyperpolarisation without causing significant damage, suggesting a protective effect. Conclusion: This study demonstrates that ACV has a dual effect in a concentration-dependent manner. ACV is an effective antifungal agent against the most common dermatophytes, acting by disrupting cell integrity, but at high concentrations, it can be cytotoxic to human keratinocytes. These findings suggest that ACV has a therapeutic effect and support its potential as a topical antifungal treatment, but need optimising concentrations to balance efficacy and safety. Major Findings: Apple Cider Vinegar (ACV) effectively inhibits the growth of most major dermatophytes at low concentrations (1.56% - 3.12%). Results highlight ACV’s potential as a topical treatment.