Formulation of a Cannabinoid-, Prebiotic-, and Postbiotic-Based Face Serum—A 30-Day Pilot Study on Skin Hydration and Aging Parameters

This study aimed to formulate and evaluate a facial serum containing Cannabis extract, a prebiotic blend of glycerin, lactitol, and xylitol, as well as heat-treated Lactobacillus plantarum HEAL19, a non-viable probiotic-derived ingredient (postbiotic) that preserves beneficial structural components and biological activity. Additionally, alternative preservatives were tested to replace conventional ones, aligning with environmentally and consumer-friendly cosmetic trends. The formulation underwent stability testing, physicochemical analysis, and microbiological control, including a challenge test to assess preservative efficacy. The efficacy of the formulation was investigated through a randomized, placebo-controlled pilot study involving sixteen healthy female volunteers aged 24–53 years. Participants were instructed to apply the active serum to one side of the face and the placebo preparation to the opposite side twice daily for a period of 30 days. Study endpoints were evaluated through clinical measurements of transepidermal water loss (TEWL), skin hydration, elasticity, and skin surface topography, together with participant-reported outcome questionnaires. Results demonstrated that the formulation possessed suitable physicochemical properties and microbiological stability. The serum was well tolerated and improved skin hydration. Participants reported enhanced esthetic appearance and perceived efficacy. These findings support the potential of combining innovative active ingredients with alternative preservatives in skin-friendly cosmetic formulations.