Inhaling eucalyptus essential oil may help to alleviate discomfort. Many anti-inflammatory chemicals, such as cineole and limonene, are found in eucalyptus and may work as pain relievers (12). Inhalation of eucalyptus oil may also help prevent bacteria or viruses from attaching themselves to your respiratory system. Although more research is needed on the effects of eucalyptus oil inhalation, this study shows that it may be safe and effective for treating coughs. Eucalyptus oil is considered safe when used as directed on product labels. However, it may cause some people to feel dizzy or sleepy in large doses or if used for long periods. If you have concerns about a particular use of eucalyptus oil, consult with a healthcare professional. Essential oils are natural substances produced by plants. They contain a complex mixture of chemical compounds including alcohols, aldehydes, acids, esters, phenols, carbonyls, terpenes, and other compounds. The aroma gives flavor to food and provides essential protection against insects and microorganisms. Essential oils are used in medicine and hygiene products because of their antimicrobial, antiseptic, and insecticidal properties.