44 J. Cosmet. Sci., 74, 44–62 (January/February 2023) Address all correspondence to Ana Raquel Madureira, rmadureira@ucp.pt The Multidisciplinary Process of Developing an Alcohol- Based Hand Sanitizer from Scratch CLÁUDIA CASTRO, INÊS PINTO-RIBEIRO, ISABEL PEREIRA, MARIA JOÃO CARVALHO, CLÁUDIA POPOV, DIANA TAVARES-VALENTE, HELENE R. MOREIRA, JOÃO C. FERNANDES, MANUELA PINTADO AND ANA RAQUEL MADUREIRA Amyris Bio Products Portugal Unipessoal Lda., Porto, Portugal (C.C., I. P-R., I.P., D. T-V., H.R.M., J.C.F., A.R.M.) Universidade Católica Portuguesa, CBQF -Centro de Biotecnologia e Química Fina – Laboratório Associado, Escola Superior de Biotecnologia, Porto, Portugal (M.J.C., C.P., M.P.) Accepted for publication May 25, 2023. Synopsis Alcohol-based hand sanitizers (ABHS) have always been used in settings that require rigorous hand hygiene, but due to the COVID-19 pandemic, they are now also used by the general population. Considering the increase in demand for ABHS, the goal was to develop a formulation with plant-based and eco-friendly ingredients without compromising performance. Several formulations were developed, and ABHS F#8 was the final result. Skin hydration, transepidermal water loss, and pH were measured in vivo after application of this formulation. An improvement in skin hydration and capacity to retain water — and a normalization of the pH to 5.7 — were observed. The ABHS antimicrobial efficacy was assessed following European standards, and the formulation was classified as bactericidal, virucidal, and yeasticidal. To confirm the formulation’s safety for daily use, two tests were performed: an in vitro skin irritation test and an ex vivo topical application followed by a cell viability test. F#8 was considered nonirritant and safe for the epidermis and dermis. The formulation was submitted to a sensory consumer evaluation in a hospital and was considered better than the benchmark. In conclusion, the authors developed a formulation with plant-based emollients that has antimicrobial activity while improving skin health and is sensorily pleasant to consumers. INTRODUCTION The skin of the hands protects individuals against infectious organisms and toxic agents, but it is also responsible for the transfer of microorganisms between people and surfaces (1). Therefore, hand sanitizers are widely used in hospitals and other occupational settings that demand frequent hand hygiene (e.g., food production settings). There are several types of hand sanitizers, but alcohol-based hand sanitizers (ABHS) are among the most commonly used and effective ones, due to their rapid antimicrobial efficacy, convenience of use, and good tolerance on the skin (2). These hand sanitizers can be more effective than traditional hand washing with soap/detergents, because they require less time for application, are faster

45 MULTIDISCIPLINARY PROCESS OF HAND SANITIZER acting, and are less irritating to the skin. This leads to more adherence to frequent hand hygiene and, consequently, a decrease in infection rates (3). Formulations of ABHS contain ethanol, isopropanol or n-propanol (or a combination thereof), and emollients, humectants, viscosity enhancers, fragrances, and colorants (4). The antimicrobial activity of ABHS results from the alcohol’s ability to denature proteins and depends on its percentage, being that solutions with 60% to 80% alcohol are the most effective (5). ABHS can damage skin and provoke irritation and/or dryness, which can cause the skin to crack or peel. However, adding emollients and humectants to the formulations helps to alleviate these symptoms (2). Emollients leave the skin looking and feeling soft and smooth and may benefit those that suffer from skin conditions such as eczema, psoriasis, or other inflammatory skin diseases (6). Humectants attract moisture to the skin surface, which helps to prevent skin drying with frequent use of ABHS (7). The COVID-19 pandemic threatened public health and resulted in a significant increase in the usage of ABHS in homes, public places, and health-care systems by the overall population (4). Although there are several ABHS formulations available in the market, they do not all correspond to the consumers. They prefer formulations that use natural ingredients with active functions on their skin and are obtained from sustainable and environmentally friendly sources (8). An excellent way to achieve this is to use plant and/or food waste (skins, seeds, stems, leaves, pulp, and other types of waste). This will produce new active ingredients/compounds with a high value in different industrial fields, such as nutraceutics, pharmaceutics, and cosmetics (9). This approach allows the substitution of synthetic chemicals and active ingredients deriving from animal sources for effective, inexpensive, and biosustainable plant- based ingredients (8,9). The main objective of this research work was to develop an ABHS with sustainable and plant- based ingredients that could protect the skin and keep it healthy without compromising antimicrobial activity. Several formulations were tested on volunteers to determine their impact in skin parameters—including hydration, transepidermal water loss (TEWL), and pH—and their sensorial characteristics. The final formulation was analyzed to verify its safety and antimicrobial efficacy. MATERIALS AND METHODS PRODUCT DEVELOPMENT PROCESS The target product was an ABHS with sustainable resourced ingredients and dermoprotective properties. Table I shows the functional, sensorial, and physical quality factors that were important for the final product formula and how these factors were evaluated. The materials used for the ABHS formulations were 96% ethanol (Labchem, Zelienople, United States CAS: 64-17-5), polyethylene glycol (PEG)-40 hydrogenated castor oil (Kao Corporation, Tokyo, Japan CAS: 61788-85-0), PEG-7 glyceryl cocoate (Kao Corporation, Tokyo, Japan CAS number: 68201-46-7), polyacrylate crosspolymer-6 (SEPPIC, Courbevoie, France CAS: 1439374-06-7), glycerin (Acofarma, Terrassa, Spain CAS: 56-81-5), cetyl alcohol (Lotioncrafter, Eastsound, United States CAS: 36653-82-4), squalane (Aprinnova, Emeryville, United States CAS: 111-01-3) and hemisqualane (Aprinnova, Emeryville, United States CAS: 3891-98-3).