Citrus essential oils, including lemon essential oil, have long been used widely in aromatherapy and alternative medicine. This study was designed to assess the effects of flavour components in lemon essential oil on physical and psychological stress. In this evaluation, acute cold stress and communication box techniques were used to apply stress after intraperitoneal administration of essential oil components such as limonene, γ-terpinene and citral. Serum corticosterone and monoamines in brain tissues were then determined. In the present study, it found the presence of perillic acid, a limonene metabolite, at concentrations of 1.5–2.5 μg/mL in serum and 0.4–0.6 μg/g in brain tissue collected 3 h after administration. The research also showed that the lemon components R-limonene, citral and γ-terpinene inhibited elevation of serum corticosterone levels and cerebral monoamine levels. S-limonene, a stereoisomer of R-limonene, seemed to have stronger effect than other monoterpenes and inhibited brain monoamines elevation on psychological stress. These findings suggest that limonenes, and particularly S-limonene, have a potent stress-alleviating effect, and the possibility that different stereoisomers of limonene have different levels of activity in their effect on stress responses. These results suggest a possibility that ingestion of lemon essential oil containing components such as limonene and citral alleviates both physical and psychological stress. Copyright © 2007 John Wiley & Sons, Ltd.