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Essential oils can be traced back to ancient times, when people used them to make medicinal ointments, perfumes and possibly embalming fluids. While we may no longer use them to mummify loved ones, essential oils have made a major comeback in recent years as a popular and powerful natural-healing solution to various ailments and conditions.

Many people say the plant-based oils — like lavender, mint and eucalyptus — are magical healers. Some people on the internet who say they have cancer claim they traded in chemotherapy for essential oils, and say their disease went into remission only after they made the switch. (PSA: Don’t do this.) Others say essential oils relieve their migraines more swiftly than over-the-counter drugs. Some people say oils boosted their libido when nothing else seemed to do the trick.

Of course, it’s hard to invalidate any one person’s personal experience if they say something personally helped them. However, despite the widespread claims made for essential oils, there is little science actually backing up the testimonials and not much is known about how safe and effective these products are.

Sure, the oils may smell delicious ― and the occasional whiff won’t do you any harm and may even help certain issues in the moment ― but many experts say they don’t live up to all the health claims.

What are essential oils, exactly?

First, a quick science lesson. Essential oils come from plants. They’re extracted from various parts of the plant — think roots, leaves or seeds — and are distilled. This process creates a highly concentrated, liquified version of a plant, which many people use for aromatherapy — an alternative medicine designed to improve people’s physical and emotional health.

The oils can be applied to the skin, topically or inhaled. And each plant is tied to a specific health benefit — peppermint is believed to increase your energy, lavender may help you calm you down, jasmine is understood to lift your mood. Some scents are even touted as able to fight cancer symptoms, heart disease, infections and diabetes.

To many, synthetic pharmaceutical drugs have lost their appeal, causing people to seek out more natural, alternate treatments like essential oils, according to Felice Gersh, an ob/gyn and founder of the Integrative Medicine Group of Irvine, California.

“So many people are ill, and are looking for something to help them feel better, it’s hard for them to walk away from a simple and natural therapy such as essential oils,” Gersh told HuffPost.

There’s not much research on them or their effectiveness

Essential oils are not regulated by the Food and Drug Administration, meaning their marketing is more or less a free for all. There are few rules or regulations monitoring the production and sale of essential oils, so it’s really up to the consumer to research what they do and how well they work.

The research we do have on the oils is often based on very small or poorly designed studies, said Gary Soffer, the acting director of the integrative medicine program at the Yale Cancer Center in New Haven, Connecticut. On top of that, the bulk of clinical research has been conducted on mice, not humans — so there’s little concrete proof of all those alleged health benefits, he noted.

While some studies suggest essential oils have a tranquilizing, anti-anxiety effect and can aid sleep, the main takeaway is that the evidence is inconclusive and we desperately need more research to fully understand how essential oils interact with the body and influence certain health conditions.

The fact that so many people regularly use essential oils without proof of their risks and benefits has some health experts worried.

“The widespread use of essential oils without a substantial body of evidence to support it is certainly concerning,” Soffer said. “While they are generally safe, it can be shortsighted to simply see them as completely risk free.”

Essential oils could have a placebo effect

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Still, those who swear by the oils include health professionals. Some experts suspect this is because of a very convincing placebo effect.

One study tested this theory and found some mind trickery might be at play. Researchers exposed people to three scents — lavender, neroli and a non-scent. Regardless of what scent they were exposed to, those who were told they were smelling a stimulating scent experienced higher physiological arousal (like a higher heart rate) and those who were told they were inhaling a relaxing scent had decreased physiological arousal. Essentially, simply reading or hearing about the alleged health claims, no matter whether they’re real or not, may cause someone to experience them.

“Across many conditions, including anxiety, depression, and pain, when people believe something is helpful, they sometimes experience benefit,” explained Keith Humphreys, a psychiatrist at Stanford Health Care in Stanford, California. “Any claims of healing power beyond the placebo effect should be regarded with extreme skepticism.”

They can cause nasty side effects

In general, aromatherapy is harmless — but essential oils can pose some health risks if misused.

For example, too high a dose has been shown to contribute to tumor development. And when consumed, the oils can potentially damage the skin, liver, kidneys and other organs. Even overuse can harm the body. Too much lavender has the potential to toy with the endocrine system and cause hormonal imbalances, Soffer said.

Additionally, some brands mix the oils with chemicals and vegetable oils — and the less pure an oil, the more likely it will cause an allergic reaction or irritation, like an itchy or painful rash.

We also don’t know too much about how essential oils interact with other medications. Health experts believe they can definitely affect how certain drugs work. For example, lavender can interfere with anti-estrogen medications commonly used to treat breast cancer, according to Soffer.