Plant Essential Oils and Chronic Inflammatory Diseases: A Panoramic View of Molecular Mechanisms

Chronic inflammation, characterized by persistent low-grade immune activation, constitutes a common pathological basis for numerous chronic diseases. It is typically associated with prolonged infiltration and activation of immune cells, dysregulation of pro- and anti-inflammatory mediators, and repeated cycles of tissue injury and repair. Current therapeutic strategies mainly rely on non-steroidal anti-inflammatory drugs, immunosuppressants, and biologics; however, their long-term application is often limited by adverse effects and safety concerns. Consequently, increasing attention has been directed toward natural products with anti-inflammatory potential. Plant essential oils (EOs) are volatile secondary metabolites extracted from aromatic plants and are primarily composed of terpenoids and other low-molecular-weight aromatic compounds. Unlike non-volatile plant-derived substances such as polyphenols, curcuminoids, or edible vegetable oils, EOs possess distinct chemical properties and biological activities related to their volatile nature. Emerging evidence suggests that EOs exhibit significant anti-inflammatory, antioxidant, and immunomodulatory effects through the regulation of multiple signaling pathways and immune responses. This review specifically focuses on the role of plant essential oils in chronic inflammation and summarizes their mechanisms of action, including modulation of inflammatory mediators, oxidative stress, and immune-cell activity. Clarifying the multi-target mechanisms of EOs may provide novel insights into the prevention and management of chronic inflammatory disorders.