The psychopharmacological outcomes of Citrus sinensis and Citrus aurantium essential oils after human inhalation

Essential oils (EOs) from citrus peels are primarily volatile terpenoids (VTs). They are complex substances with actions on Central Nervous System (CNS), inducing sedative, anxiolytic, and other effects. The objective was to evaluate the psychopharmacological effects of inhaling mixed citrus EOs - rich in VTs - in humans. These EOs are traditionally used by the Brazilian population. A double-blind randomized controlled (RCT) trial with 75 volunteers divided into three groups was carried out. The experimental group inhaled a mixture of citrus EOs, composed of sweet orange peel Citrus sinensis (L.) Osbeck and bitter orange leaves Citrus x aurantium L. The study was conducted for six months, with healthy adults in Porto Alegre, Brazil. The volunteers were evaluated through psychometric protocols and biochemical parameters by saliva analysis. The CONSORT Flow Diagram was employed to report RCTs of aromatic interventions. Improvement in some of psycho-emotional health symptoms was demonstrated, correlated with increased salivary levels of Leptin, and decreases in IL-2, IL-6, and TNF-alpha. The results suggested the existence of an improvement in biochemical parameters and psycho-emotional symptoms after inhalation of citrus EOs rich in VTs. This study comes in line with traditional usage and the empirical knowledge of ancestral cultures Brazilian population. It may contribute to supporting the idea that the inhalation of natural products can improve psycho-emotional states with positive repercussions on the immune system. [Approved: network International Clinical Trials Registry Platform, ICTRP, RBR-6ktp6t9 - UTN: U1111-1332-7952, Ethical Committee Certificate of Presentation of Ethical Appreciation, number CAAE: 46098615.5.0000.5347, Federal University of Rio Grande do Sul, UFRGS, Brazil.