Cinnamon bark oil from Cinnamomum verum is defined by a high trans-cinnamaldehyde content (60-80%), which delivers a rich, sweet, and complex warmth that distinguishes it from every other member of the genus — including cassia, whose cinnamaldehyde lacks the sweeter ester notes of true Ceylon bark. It is the most commercially prized of the cinnamon oils and finds application in both high-end perfumery and functional aromatherapy blends. In vitro research confirms potent broad-spectrum antibacterial activity: the oil disrupts bacterial cell envelopes and causes leakage of intracellular contents, with documented efficacy against multi-drug-resistant Escherichia coli strains.^[1] Because cinnamaldehyde is a recognised skin sensitiser, bark oil must be used at low dilutions (typically ≤0.5% for leave-on products) and with patch-testing; comprehensive analysis also shows meaningful antioxidant and antiproliferative properties alongside its antimicrobial action.^[2]