Comparative In Vitro Evaluation of Selected Essential Oils and Commercial Blends Against Skin-Associated Pathogens

Essential oils are widely used in cosmetic products and are valued for their antimicrobial properties. In this study, the in vitro antimicrobial activity of five pure essential oils (EOs) and five commercially available EO blends was comparatively evaluated against six skin-associated pathogens: Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Candida lusitaniae and Candida guilliermondii. Chemical profiling of volatile constituents was performed using gas chromatography–mass spectrometry; antimicrobial activity was assessed by broth microdilution to determine minimum inhibitory concentration (MIC), as well as spot-inoculation to determine minimum bactericidal concentration (MBC). Results revealed microorganism-dependent inhibitory and bactericidal activity of the tested essential oils. Candida spp. and E. coli were the most susceptible microorganisms, whereas P. aeruginosa exhibited the lowest susceptibility to essential oils. Pinus sylvestris showed comparatively lower MIC and MBC values across most tested microorganisms. Commercial EO blends showed comparable antimicrobial activity to individual essential oils. Overall, this study provides a comparative in vitro screening of selected essential oils and commercial blends relevant to cosmetic applications, indicating that EO blends do not exhibit superior antimicrobial activity over pure oils under the tested conditions.