489 Apple cider vinegar: a promising adjunctive anti-staphylococcal treatment in atopic dermatitis

Apple cider vinegar (ACV) is touted in popular press as a natural remedy for eczema. Though commonly used by wound care professionals, little data exist regarding the clinical use of ACV in atopic dermatitis. One potential mechanism of action of ACV to benefit atopic dermatitis could be an antimicrobial effect against Staphylococcus aureus. Since dilute bleach baths have recently been shown not to kill Staphylococcus aureus, we examined whether food-grade 5% acidity ACV has antimicrobial effect against Staphylococcus aureus after a ten-minute exposure. Bactericidal effect of food-grade 5% acidity ACV against Staphylococcus aureus was equivalent to that of full-strength Clorox bleach (sodium hypochlorite 6% solution) after ten minutes. Three-log bactericidal activity against Staphylococcus aureus was seen at a 3/4 dilution of ACV compared with distilled water (p=0.02). The minimum dilution of apple cider vinegar required for significant growth inhibition of Staphylococcus aureus, compared with distilled water, following a ten-minute exposure was 1/256 (pH ∼3.5) (p=0.02), which is equivalent to 1 tablespoon of ACV in 1 gallon of water, or 2.5 cups of ACV in a 40-gallon bathtub. This growth inhibition was reversed by dilution of ACV in Bis-Tris buffer (pH ∼6.5) instead of in distilled water, suggesting a pH-dependent mechanism. Bactericidal activity despite presence of Bis-Tris was again observed at a 3/4 dilution of ACV (pH ∼2.6) (p=0.01), suggesting Staphylococcus aureus’s robust pH defense mechanisms fail around a pH of 2.6. Dilute food-grade 5% acidity ACV demonstrates anti-staphylococcal activity after as little as ten minutes. Further studies are warranted to determine if ACV could potentially be used as an adjunctive and/or local anti-staphylococcal treatment in atopic dermatitis.