The rise of the wellness industrial complex has put things like natural beauty and essential oils in the spotlight for their perceived lack of chemicals.

Though common in skincare and household cleaning products today, essential oils have long been revered for their healing powers and are used for health and medicinal purposes such as alleviating anxiety or curing the common cold. In fact, a cursory glance at the web results for “essential oils” tells the story of a magical cure-all — one most vehemently told by the multi-level marketing companies that sell them.

But when it comes to the science-backed benefits of essential oils, what’s actually effective? According to experts and research, not much. Here’s what you should know before you invest.

What are essential oils?

Essential oils are not vital to humans, as their name might suggest. They’re compounds extracted from plants through a distillation or cold-pressing process that captures the plant’s “essential” scent and flavor.

Known for demystifying chemistry, Joe Schwarcz, director of McGill University’s Office for Science and Society, explains that many plants’ compounds are volatile: “Some [are] destined to attract pollinators, others to ward off bugs that have the intention of making a tasty meal of the leaves. It is the volatile chemicals that are regarded as the plant’s essence and are the ones captured in the ‘essential oil.’”

(In fact, another name for essential oil is “volatile oil.”)

How they’re used

Today, essential oils are used to add scent to cosmetics and cleaning products, and flavor to food and beverages, Schwarcz says; but they’re also used as “medical treatments by application to the skin, through ingestion, or through inhalation, the latter commonly being referred to as ‘aromatherapy.’”

Essential oils have a long history of use. They were used for thousands of years in cosmetics and perfumes and for therapeutic purposes by ancient cultures from China and India to the Egyptians and Romans.

Dilini Vethanayagam, an internist and associate professor of pulmonary medicine at the University of Alberta, says Western countries are simply new to the trend. “I’m originally from South Asia, and alternative medicines are very popular there, but that’s over many decades of training,” she notes.

It’s undeniable that it’s a booming business right now, thanks in part to billion-dollar companies selling essential oil products. Rachel Monroe reported for The New Yorker last fall that in 10 years, essential oil company Young Living grew tenfold. Its competitor doTERRA claimed it made $1 billion in sales in 2015.

As Monroe theorized, people today are turning to essential oils because they’re disillusioned by Western medicine. And as Annaliese Griffin recently speculated in Quartz, women are doing so in particular, since modern medicine and the U.S. healthcare system has failed them time and time again:

“The medical system is even more terrible for women, whose experience of pain is routinely minimized by health practitioners. … Enter the wellness industry, which specializes in creating safe, welcoming, amber-lit spaces that make people feel cared-for and relaxed, and which treats the female body as its default. … The problem is that the rest of the wellness industry hitches a ride on their coattails of compassion and competency, benefiting from the utter lack of warmth found in mainstream medical treatment.”

So, what are the claims?

Lavender oil is good for skin irritations, easing muscle tension and helping with sleep problems. Rose oil cures acne and increases sex drive. Sweet orange oil controls gas and stomach problems.

There seems to be an essential oil solution for just about every condition and problem. Guides on the topic are common on health and natural living blogs, but even institutions like the University of Maryland Medical Center offer reference guides for aromatherapy.

Many of the claims about essential oils come from studies showing that their chemical compounds have certain benefits — like tea tree oil, which has antibacterial and antifungal properties. But just because it has antibacterial properties doesn’t mean it can necessarily cure your acne. Other circulating claims are based on studies in which essential oils were tested on rats or other animals rather than humans, or studies that were inconclusive, the results indicating a placebo effect.

In other words, the leap to suggest they can cure and treat conditions is a stretch, Schwarcz says.

Sketchy companies and marketing

In her New Yorker piece, Monroe goes into detail about Young Living (the self-described “World Leader in Essential Oils”) founder Gary Young’s questionable background, which includes opening a health center in Washington state in 1982 where his own daughter died from a birthing service in which she was submerged for an hour in a whirlpool bath; being arrested for practicing medicine without a license; and opening a clinic in Tijuana where he made false diagnoses to get patients to join a costly detox program.

Young, by the way, is a naturopathic doctor who uses natural healing to cure and treat illness. (The legitimacy of naturopathy as a practice has been criticized.)

Even taking Young out of the picture, the business model for these companies is problematic. Two of the biggest essential oil companies, Young Living and doTERRA, work as multi-level marketing schemes. Salespeople in the companies are known as distributors who buy the products at wholesale prices and mark them up to sell them to consumers. “But the real money,” Monroe writes, “comes from recruiting other distributors into your ‘downline’ and getting a commission on their sales.”

Schwarcz adds that distributors often make incredulous claims in order to make sales. “Some of the people the company has snared with its promises of wealth through multi-level marketing end up making a bevy of claims about essential oils helping with cancer, autism, Alzheimer’s disease, mononucleosis and arthritis,” he says.

An unregulated market

Like other complementary and alternative medicines (CAM), the essential oil market is unregulated. But several years ago, the Food and Drug Administration, which regulates prescription medication, issued a warning about Young Living’s marketing. After reviewing the company’s websites and social media accounts, the FDA found that the company was mislabeling and misbranding their products as drugs even though they were not approved as such.

The company had been marketing their products as cures, treatments and preventative measures for things like viral ebola, Parkinson’s disease, autism, diabetes, hypertension, cancer, insomnia, heart disease, post-traumatic stress disorder (PTSD), dementia and multiple sclerosis.

Per ATTN’s reporting, the FDA sent similar warnings to doTERRA and another company, and FDA spokesperson Lindsay Meyer informed the outlet that consumers should be wary of fraud and scams that involve claims to prevent, treat or cure health conditions. “Health fraud scams waste money and can lead to delays in getting proper diagnosis and treatment. They can also cause serious or even fatal injuries,” she told ATTN.

(The companies have also had legal troubles unrelated to product claims.)

The language on Young Living’s website and other similar companies’ websites has since softened, for example, by claiming a scent will help you “refocus.”

No proven benefits

As opposed to modern medicine, CAM is difficult to clock as pseudoscience or not, because human studies and clinical trials on things like essential oils are lacking. “If patients talk about using them as treatment,” Vethanayagam says, “I stop them right there.”

According to two studies (one in 2000 and another in 2012), there’s no convincing evidence that aromatherapy can calm hypertension, depression, anxiety, pain or symptoms of dementia. Schwarcz adds that studies shown to prove the benefits of essential oils are often not reliable, noting that “the scent of lavender may have a calming effect in some people and help with sleep, but it can cause headaches in others.”

And while it may be true that scents can be calming and pleasing to people, Pam Dalton of the Monell Chemical Senses Center says that “they likely aren’t working due to any pharmacological or biological effect, [but] rather a sensory/psychological effect.” For instance, the scent of mint may make you feel more alert because it stimulates a nerve that allows you to perceive irritation and pain (or lack thereof).

In other words, these are mood-based changes rather than physiological ones, and the evidence for the mood-based changes depend on subjective memories you have tied to particular scents. Dalton is currently working on a project funded by an essential oil company, but she says she’s still a skeptic.

In addition, in most studies looking at the benefits of aromatherapy on cancer patients as complementary to chemotherapy and other treatments, the results are mixed.

Dermatologist Diane Berson, who recently spoke at a conference about essential oils as a cosmeceutical trend, says they’re typically okay to use in skincare products if you don’t have an allergic reaction to them. Many people use them since they’re advertised as “botanicals,” but she says there’s no evidence that these are any better than ingredients made synthetically.

Are they dangerous?

Most essential oils are generally considered safe to inhale or apply topically, but be aware that they can cause different reactions in different people, Vethanayagam cautions.

Some people with underlying health conditions might experience problems. A 2013 study she authored, focused on fragranced household items, confirms this. “In an open air environment, if you whiff an aroma, maybe it doesn’t cause negative issues,” she says, “but if you have asthma, it can have a negative impact. It can either be an irritant effect or an inflammatory effect.”

Vethanayagam, whose practice focuses on allergies, says this can potentially cause damage to the hairlike projections, or cilia, that line our airways. As for ingesting? Vethanayagam says it’s probably okay in small quantities. “The lungs are very sensitive, but the stomach goes through many processes to take out the bad stuff,” she says. Berson warns that “some ingredients do cause dermatitis or negative reactions, and some common ones that cause allergic reactions are tea tree oil, lavender, peppermint.”

The University of Maryland Medical Center states that, in general, essential oils should not be used during pregnancy.

The bottom line: Essential oils smell nice, but there’s no evidence they work. In fact, depending on your sensitivity to fragrance and your past medical history, they might even be irritating.

If you enjoy how they smell and still want to use them, go ahead! “If the smell of lavender relaxes you for whatever reason, sniff it at bedtime when you find it difficult to disengage,” Dalton says. “If the smell of wintergreen makes you feel more energized, take a whiff when you’re heading off for a run on the treadmill.”

But you’d be wise to be aware of their limitations and — perhaps more importantly — of the companies that stand to profit from understating them.

Photos by Louisiana Mei Gelpi. Photos feature UMA oil kits and a Bel Air Naturals oil kit.