Objective

The human axilla is colonized by a wide array of microorganisms that contribute to the generation of body odor. Traditional antiperspirant/deodorant products are used to reduce perspiration in the axillary region and to treat or prevent the growth of bacteria in this region, thereby reducing or eliminating body odor. However, they may also compromise the axillary microbiome balance. The personal care industry has been seeking new ingredients, such as prebiotics or probiotics, to maintain a healthy balance of the skin microbiome by inhibiting odor-causing bacteria while maintaining and promoting the growth of good bacteria. The aim of this study was to investigate the prebiotic effect of a skin care ingredient, 2-butyloctanol, on the human axillary microbiome.

Methods

An in vitro growth inhibition/promotion assay was performed to test whether 2-butyloctanol inhibited or promoted skin bacterial growth. The impact of 2-butyloctanol on the axillary microbiome was also investigated in a human clinical study using 16S rRNA gene sequencing.

Results

In vitro testing showed that 2-butyloctanol significantly inhibited the growth of corynebacteria at concentrations of 0.64%, 2.56%, and 5.12%, while the growth of Staphylococcus epidermidis was maintained at the same concentrations. The impact of 2-butyloctanol on the axillary microbiome was also validated in a human clinical study. A deodorant roll-on product containing 3% 2-butyloctanol significantly reduced the relative abundance of corynebacteria while increasing the relative abundance of Staphylococcus and the ratio of Staphylococcus to corynebacteria after four weeks of application, while the placebo showed no significant change.

Conclusion

For the first time, it was demonstrated that 2-butyloctanol had a potential prebiotic effect on the human underarm microbiome in inhibiting odor-causing Corynebacterium while maintaining and promoting skin-friendly Staphylococcus in both in vitro and in vivo studies. Therefore, 2-butyloctanol could be used as a potential prebiotic ingredient in personal care products for underarm microbiome protection.