Scalp Microbiome and Dandruff—Exploring Novel Biobased Esters

Recent data suggest that dandruff might be associated with dysbiosis of the scalp microbiome. This mini review summarizes the microbiome changes seen with the dandruff condition, as well as different solutions for dandruff control and their effects on the scalp microbiome in relation to in vivo efficacy. Since zinc pyrithione has been banned from cosmetics in the EU, the medium-chain fatty acid ester propanediol caprylate is a new option, in addition to the remaining conventional ingredients: piroctone olamine, climbazole, and salicylic acid. The ester is rapidly cleaved by Malassezia hydrolases in the external milieu, thereby releasing active caprylic acid. In addition to its auto-regulatory effects on Malassezia, propanediol caprylate is also able to influence the bacterial microbiota towards a healthier scalp microbiome. In vivo data have shown an efficacy comparable to climbazole and piroctone olamine. In vivo additive and synergistic effects in different combinations allow reductions in the concentration of conventional agents. Surprisingly, a new effect of a lasting healthier scalp has been identified in connection with ester use, in contrast to the usual return of dandruff experienced upon the discontinuation of anti-dandruff shampoo with conventional actives. We also report on new data from an unpublished comparative study on two propanediol monoesters confirming the long-lasting effect.