Abstract
BACKGROUND: Spent coffee grounds (SCG) offer significant ecological and cosmetic potential. The conversion of SCG into safe and efficient cosmetic products promotes all aspects of sustainability and circular practices within the cosmetic industry. AIMS: This study aimed to show the interdisciplinary bottom-up approach within two focal points: demonstrating the use of upcycled materials in high-value natural products and understanding how base formulations' content and properties influence the characteristics, consumer preferences, and clinical efficacy of exfoliant products. METHODS: Methods included characterization of SCG, development of formulations, physicochemical characterization, stability testing, and the estimation of carbon dioxide emissions of the preparation process. Consumer panel testing optimized the most preferred sensory characteristics of exfoliant products chosen for clinical evaluation. Transepidermal water loss measurements assessed skin barrier disruption and recovery after the use of exfoliant formulations and after the application of hand cream. RESULTS: The SCG found richest in bioactive substances was incorporated in three concentrations into seven exfoliant formulation bases. Stable formulations were assessed by a consumer panel, and four formulations with the best sensory characteristics were ointment-based (F1) with 5% and 10% SCG, cream-based (F6), and gel-based (F11) with 5% SCG. The ointment-based exfoliant showed no significant changes after application or after hydration cream. Aqueous formulations (F6 and F11) temporarily disrupted skin barrier function, but full recovery occurred within 6 h of hand cream application. CONCLUSION: By utilizing SCG, high-quality cosmetic formulations can be created that are well-received by consumers. Clinical findings suggest that different exfoliant formulations may suit various skin types.