Cinnamon and cinnamon oil are spices derived from tropical plants with a long and well-established use in food and fragrances. The main biologically active substances in cinnamon are cinnamaldehyde and eugenol, although others also appear to have significant activity. As a pesticide, cinnamon’s main mode of action with insects appears to be as a repellant, although it has biocidal action at higher doses. Phytotoxic effects of cinnamon make it a possible herbicide, but also limit its practical foliar application to crops. Cinnamon and its essential oils are antimicrobial in nature and are effective at inhibiting the growth of bacteria and fungi. While cinnamon and cinnamon oils may cause skin irritation, the EPA allows their use as active ingredients in pesticide products that are exempt from registration. The EPA considers them exempt from the requirement of a tolerance on the various food crops to which they are applied.