Essential oils: What are they, and do they work?

Curious about using essential oils for aromatherapy or skincare? Read on for a deep dive into the science behind the health claims.

By Lindsey Emery

Published January 28, 2021

For centuries, people around the world have tapped into the healing power of plants. And recent years have brought a boom for one botanical product category in particular: essential oils. These concentrated plant extracts don’t just smell nice, proponents say—fans contend that some oils may also boost energy, bring calm, reduce inflammation, even erase pain.

How does the science stack up regarding these claims? Read on for a closer look at the potential benefits, risks, and uses of essential oils.

What are essential oils?

An essential oil is an aromatic liquid extracted from a plant. The oil comprises hundreds of chemical components, with a unique scent shaped by factors such the growth environment of the source plant.

Except for essential oils of citrus fruits (which are cold-pressed), essential oils are generally extracted by steam distillation—steaming and pressing the plant to capture the compounds that produce fragrance. The resulting product is very concentrated: It can take several pounds of a plant to produce just 15mL of essential oil.

Popular essential oils include eucalyptus (eucalyptus globulus), lavender (lavandula), rose (rosa damascena), peppermint (mentha piperita), tea tree (melaleuca alternifolia), lemon (citrus limonum), and bergamot (citrus bergamia).

Synthetic oils mimic the aroma of essential oils but may not contain plant compounds. To tell if an oil is the real deal, check the bottle’s label, says aromatherapist KG Stiles, author of The Essential Oils Complete Reference Guide. It should state that the product is 100% essential oil, as well as list the country of origin. Look for an essential oil packaged in a tinted glass bottle, Stiles advises, as exposure to sunlight and plastic packaging can degrade an oil’s quality.

Essential oils for aromatherapy

Essential oils are typically used for aromatherapy, the practice of inhaling scent for a desired therapeutic benefit. If you’ve ever caught a whiff of a loved one’s perfume and instantly gotten warm and fuzzy feelings, you’ve experienced the power of scent. “When you smell an essential oil, it goes straight to your brain,” Stiles says. Scent molecules are picked up by specialized structures in the nose that relay a message to the brain; this, in turn, may set off changes in neurotransmitters.

To use an essential oil for aromatherapy, don’t stick your nose into the bottle (you wouldn’t want to inhale the liquid by accident!). “Put two drops of oil on a cotton ball, and take a couple deep breaths through your nose,” Stiles suggests. Or use a diffuser that disperses fragrance diluted with water vapor into the air.

Other uses of essential oils

Essential oils are commonly used to scent skincare and beauty products. Some people enjoy placing a few drops of lavender, eucalyptus, or peppermint oil into a shower or bath; others like to add a citrus essential oil to homemade cleaning products.

Benefits of essential oils: Fact or fiction?

You may have heard that essential oils can help you sleep, find calm, and control pain and inflammation. While early research is promising for some of those claims, larger-scale studies are needed in most cases to see if the evidence holds up. Here’s a deeper dive into the science of essential oils:

Claim 1: Essential oils reduce stress and anxiety

The jury’s out on whether pleasant-smelling oils can induce calm. Some studies have found an association between the scent of lavender essential oil and reduced anxiety. Meanwhile, a small pilot study in 2017 suggested that the scent of bergamot oil may spark a positive mood. That said, a major scientific review of existing research in 2019 concluded that evidence on the effect of essential oils on stress and anxiety isn’t yet strong enough to support a recommendation for using them.

Claim 2: Essential oils boost energy

Trying to beat the afternoon slump? The scientific review cited above found some evidence that lavender may reduce fatigue in people undergoing hemodialysis, whereas other studies did not find an energizing effect. Again, confidence in evidence from scientific review of studies looking at the effect of essential oils on fatigue was low.

Claim 3: Essential oils alleviate menstrual pain

There’s some evidence to suggest that a few drops of essential oils such as lavender, peppermint, or rose may help relieve period cramps when massaged onto the abdominal area with a carrier oil. More research is needed to better understand the possible mechanisms at play.

Claim 4: Essential oils reduce inflammation

Research on the anti-inflammatory effect of essential oils has mainly been conducted in the lab and focused on bowel inflammation in rats. According to the National Association for Holistic Aromatherapy (NAHA), ginger and patchouli oils have anti-inflammatory properties; what’s needed are good quality studies on people to see if such claims hold up.

Claim 5: Essential oils relieve congestion

Adding oils like eucalyptus, lavender, or peppermint to a steam inhaler adds a pleasant fragrance to water vapor, but there’s no published evidence to show that essential oils themselves clear blocked nasal passages. (Steam alone can do that.) One study of 54 adults suggested that the scent of an essential oil blend—sandalwood, geranium, and Ravensara—may alleviate some symptoms of nasal allergies, but the study was small, lasted just seven days, and didn’t directly measure biomarkers associated with allergic symptoms.

Potential side effects and risks of essential oils

Essential oils are generally safe when used correctly, but that doesn’t mean they cannot cause harm. Never add them to food or drinks, and always check the product label for a list of potential side effects. The most common include:

Rash: Essential oils are super concentrated. Oils themselves, as well products that contain them, may irritate sensitive skin. If you develop a rash, wash the area with gentle soap and water. If your symptoms persist or worsen, contact your doctor.
Allergic reaction: If your skin feels itchy, burns, or breaks out in hives after using an essential oil, contact your doctor—you may be having an allergic reaction.
Headache: Prolonged exposure to essential oil vapor can trigger headaches and nausea, according to the NAHA. If you’re using a diffuser, consider limiting its run time to 30 minutes and use the minimum amount of oil suggested for the device.
Sun sensitivity: Some oils, such as those derived from citrus fruits, can make skin more sensitive to the sun. If you’re using skincare products that contain essential oils, be sure to apply a broad-spectrum sunscreen, as well.

The upshot: Do essential oils work—and should you try them?

Scientific research on the health benefits of essential oils is limited. The U.S. Food and Drug Administration does not classify essential oils as medicinal agents because they haven’t met the agency’s standards for effectiveness. To date, some smaller studies have suggested that certain essential oils may have some benefits. More good-quality research is needed to support broad recommendations for use.

Essential oils are generally considered safe for aromatherapeutic, topical, and household uses when used as directed, though some people may experience side effects such as headaches or skin irritation. Essential oils are not formulated for ingestion, so do not add them to food or drinks. If you decide to try an essential oil, purchase from a reputable source and read the product label carefully.

Lindsey Emery is a freelance writer and editor who has been covering health, fitness, sports, nutrition, and gear for almost 20 years. She lives in Portland, Oregon, where she spends most of her time chasing two happy toddlers and their giant dog.

This article was reviewed for accuracy in July 2021 by Megan Schreier, MPH, senior manager for behavior change science translation at WeightWatchers®. The Science Team is a dedicated group of experts who ensure all our solutions are rooted in the best possible research.