Pharmacologic effects approach of essential oils and their components on respiratory diseases

Essential oils (EOs) are concentrated hydrophobic liquids with volatility and a unique aroma. Formed by aromatic plants as secondary metabolites, EOs have been used as traditional medicines to treat various health problems worldwide. Historical records show that herbs rich in EOs have been widely used to treat respiratory diseases in China, Europe, and many other regions. This review summarizes the traditional applications and modern pharmacological mechanisms of EOs derived from aromatic herbs and their active ingredients in respiratory diseases in preclinical and clinical trials through multitarget synergy. Information about EOs and respiratory diseases was collected from electronic databases, such as ScienceDirect, Web of Science, PubMed, Google Scholar, Baidu Scholar, and the China National Knowledge Infrastructure (CNKI). This review presents the preventive and therapeutic effects of EOs on respiratory diseases, including chronic obstructive pulmonary disease, bronchial asthma, acute lung injury, pulmonary infection, and pulmonary fibrosis. The molecular mechanisms of EOs in treating different lung diseases are summarized, including anti-inflammation, anti-oxidation, mucolytic, and immune regulatory mechanisms. EOs show potential as supplements or substitutes for treating lung diseases.