14 J. Cosmet. Sci., 74, 14–30 (January/February 2023) Address all correspondence to Mehzat Altun, mehzataltun@comu.edu.tr Chemical Characterization, Antibacterial, Antioxidant, and Cytotoxic Activity of Some Essential Oils Against Strains Causing Acne MEHZAT ALTUN, NURAY YILDIRIM AND BINNUR M. YAPICI Canakkale Onsekiz Mart University, Canakkale, Turkey (M.A., N.Y., B.M.Y.) Accepted for publication May 24, 2023. Synopsis The potential of essential oils (EOs) as alternatives to antibiotics for the treatment of acne vulgaris is an area of growing interest due to increasing antibacterial resistance. This study aimed to determine antimicrobial efficacy, chemical profile, and the antioxidant and cytotoxic potential of EOs. Antimicrobial activity was assessed using disc diffusion and minimum inhibitory concentration (MIC) assays against Staphylococcus epidermidis ATCC 12228 and Cutibacterium acnes ATCC 6919. The phytochemical content of oils was determined by gas chromatography/mass spectrometry. The 2,2-diphenyl-1-picrylhydrazyl and the 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide methods were used to detect antioxidant properties and cell viability, respectively. Limonene, p-cymene, linalool, 1.8-cineole, β-santalol, cinnamaldehyde, carvacrol, and eucalyptol were the major components of lemon, tea tree, lavender, laurel, sandalwood, cinnamon, oregano, and eucalyptus EOs, respectively. The MIC/minimum bactericidal concentration values were between 0.03125% and 32% (v/v). Binary combinations of cinnamon/lavender and cinnamon/sandalwood exhibited synergism against both bacteria. The Cinnamomum verum showed the greatest antioxidant activity (IC50: 35.08 µg/ml). The cytotoxic activity of EOs at concentrations between 2% and 0.0625% was evaluated against a mouse fibroblast (NIH 3T3) cell line. In vitro test results revealed that antibacterial effective EOs may be used in development of topical acne therapy after in vivo and clinical trials are carried out. INTRODUCTION Acne vulgaris involving the pilosebaceous units (hair follicle and sebaceous glands) is a chronic inflammatory skin disease that affects approximately 650 million people worldwide (1,2). Acne is seen in about 80% of the 11–30 age group and 20% of adults over the age of 30. Individuals with acne are negatively affected socially and mentally (3–5). Increasing sebum production, cornification of sebaceous glands and excretory ducts releasing inflammatory mediators, and enlargement of the bacterial flora in the skin constitute the pathogenesis of patients with acne vulgaris (3). Cutibacterium acnes, formerly Propionibacterium acnes, and Staphylococcus epidermidis are members of normal human skin microbiota and are named acne-associated pathogens (6).