Cassia oil (Cinnamomum cassia) is cinnamaldehyde-dominant at 75-90%, but delivers a noticeably harsher, more astringent character than C. verum bark oil due to its virtual absence of the sweeter esters (benzyl acetate, cinnamyl acetate) found in true Ceylon cinnamon; this is the variety underpinning most of the world's commercial 'cinnamon' food flavouring. It stands among the most potent essential oils tested for antimicrobial activity: in vitro studies record broad-spectrum inhibition of bacteria, yeasts, moulds, and dermatophytes at low concentrations, with cinnamaldehyde identified as the primary bioactive agent.^[1] Clinical-relevance is underlined by demonstrated synergistic antibacterial activity against carbapenemase-producing Klebsiella pneumoniae when combined with polymyxin B, pointing to potential utility against difficult drug-resistant pathogens.^[2]