Your quest to solve a number of health ailments - anxiety,EAI Community  insomnia, nausea and more - may have brought you to look up essential oils.

They're usually sold in small, dark-colored bottles and have varying potent scents. But what actually are essential oils? Are they good for you? Here's what medical experts want you to know before trying them.

What are essential oils?

Essential oils are fragrant plant extracts, made by steaming or pressing plants, according to Johns Hopkins Medicine. They're often used for aromatherapy, which a centuries-old practice of inhaling these oils or absorbing them through the skin with the goal of improving certain health ailments.

What are examples of essential oils?

There are dozens of types of essential oils. Some of the most popular include lavender, tea tree, peppermint and lemon oils, per Johns Hopkins.

More on essential oilsWhat oils to use, how to use them and safety tips

Are essential oils good or bad for you? 

Some research has shown that essential oils can offer some benefit for some health concerns. Lavender essential oil may be beneficial for anxiety, depression and sleep; peppermint and ginger may help subside nausea and vomiting.

But experts caution that there's still a lot unknown about how essential oils work, because most of the studies conducted aren't the highest quality.

"Conducting high quality research with essential oils can be challenging," University of Maryland School of Pharmacy assistant professor Lauren Hynicka, PharmD, BCPS, tells USA TODAY. She references double-blind studies, during which neither the study subject nor the researcher knows if a placebo or actual treatment is being used until the end to prevent bias.

But as Hynicka points out, it's tough to fake a placebo for essential oils: "Either you smell an essential oil, or you don’t."

Johns Hopkins called some lab studies "promising," but said clinical trials actually using humans were "mixed," with some showing benefits and others showing no improvement in symptoms.

If you're going to use an essential oil, Hynicka says they're likely safe when inhaled, such as adding a few drops to a diffuser, cotton ball or nasal inhaler. If you're going to use them topically, dilute them in coconut or jojoba oil first. And make sure you're investing in a high-quality essential oil — Johns Hopkins warns that some companies will dub their products "therapeutic-grade," but that's an unregulated marketing term, not a signifier that it's a product a medical expert would recommend.

"I would recommend anyone using essential oils mention the reason and how they plan to use essential oils with their doctor or medical provider," Hynicka says, adding that they should be kept away from children and pets. "It would be especially important to consult with your care provider if you are pregnant, nursing, taking medication or have a history of seizures."

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