Exploring the Potential of Cleansing Hydrogel and Shampoo with Whey as a Contemporary Approach to Sustainability.

Cosmetology is one of the fastest-growing scientific areas, and within it, individual needs and preferences have to be considered. Specifically, cosmetic products with incorporated biological macromolecules, i.e., proteins and peptides, that contribute to improved skin features are gaining in importance. Similar to other fields, cosmetology is also faced with the zero-waste paradigm and strives for a collaboration with other industries. Whey is a co-product in milk production and represents a high environmental burden. In this regard, the idea of the present study was to utilise whey in order to develop sustainable cosmetic products, i.e., cleansing hydrogel and shampoo. The initial phase of the study was dedicated to the development of an optimised hydrogel and shampoo base, followed by whey integration and an in-depth physico-chemical characterisation of both prototypes. In the subsequent phases, particular emphasis was placed on evaluating the potential skin irritancy of the whey-based formulations in vitro, complemented by in vivo assessment on volunteers. The results obtained indicate that the incorporation of whey at concentrations of up to 30% (m/m) is feasible for both formulation types. Moreover, neither product exhibited any irritative effects and a study on volunteers showed that whey has great potential in terms of providing adequate skin hydration. Taken together, all the findings support the development of advanced cosmetic formulations with a zero-waste concept built-in, thus offering a promising platform for cross-sector collaboration, and representing a meaningful step toward potential hydrogel and shampoo commercialisation.