In‐vivo pilot study to assess a new plant‐based cosmetic formulation containing Ziziphus joazeiro bark extract and Apium graveolens seed extract for the improvement of dandruff while enhancing scalp microbiome balance and barrier function in subjects with oily to dry sensitive scalps

OBJECTIVE: Dandruff is one of the most common dermatological conditions, which occurs in about 50% of human individuals confined only to the scalp. Microbiome studies indicate a bacterial and fungal microbiota shift compared to a healthy scalp. While antifungal treatments are effective in improving clinical signs and symptoms of scalp dandruff, maintaining a healthy scalp microbiome balance is also crucial for long-term scalp health. The objective of this study was to investigate whether a novel plant-based formula containing Ziziphus joazeiro bark extract and Apium graveolens seed extract is capable of reducing mild-to-moderate dandruff symptoms and restoring the scalp skin barrier function and its impact on the microbiota balance after a 4-week application period. METHODS: An open-label, single-centre study was performed including 40 subjects with mild-to-moderate dandruff with either oily or dry sensitive scalp. Subjects were treated for 4 weeks with a novel plant-based shampoo to demonstrate the efficacy in reduction of dandruff (scaling) and redness and stabilization of trans-epidermal water loss (TEWL). Dermatological measurements were performed as well as a scalp microbiome analysis of 20 subjects with a focus on alpha and beta diversity and abundance of core microbiota. The analysis was performed on swab samples taken prior to and 28 days after application of the product of interest. RESULTS: Clinical data revealed that the new plant-based shampoo was well tolerated. TEWL analysis showed a highly significant improvement (-18.60%, p = 0.00035). With respect to redness (-22.8%, p = 0.00127) and dandruff reduction (scaling, -29.23%, p = 0.000001), a significant improvement in the analysed parameters was also determined. Microbiome analysis revealed no significant changes in alpha or beta diversity, suggesting that the product has no negative impact on microbial diversity or affecting the overall structure of microbial communities within individuals. Interestingly, fungal species seem not to be involved in dandruff development within the analysed cohort. The key finding was a significant median increase in the Cutibacterium/Staphylococcus ratio (+19.57%). CONCLUSION: The study indicates that mild-to-moderate dandruff symptoms can successfully be reduced with the plant-based shampoo by restoring the bacterial scalp microbiome balance, suggesting a 'microbiome-friendly' formulation tolerated excellently for oily scalp and sensitive scalp.