Do Aromatherapy and Essential Oils Work? What the Research Says

Aromatherapy and essential oils are used or claimed to be useful for a vast array of symptoms and conditions. According to Fortune Business Insights, the global essential oils market is booming, with sales of $8.74 billion in 2020, and that amount is expected to more than double to $18.25 billion by 2028. While the body of research as to their effectiveness is growing, more extensive and rigorous human clinical trials are needed.

Aromatherapy, a derivative of herbal medicine, is the therapeutic use of essential oils from plants to improve the mind, body, and spirit. While aromatic (fragrant) oils have been used for thousands of years, aromatherapy as we know it is said to have been started when French chemist and perfumer Rene Gattefosse coined the term aromatherapy and published a book of that name in 1937. Aromatherapy is often used for symptom management with other complementary treatments like massage therapy and acupuncture, as well as with standard medical treatments. 

Essential oils are the aromatic part of plants, often underneath the surface of leaves, bark, or peel. When the plant is crushed or steamed, it releases the fragrance. It takes enormous quantities of plant material to make essential oils (e.g., 220 pounds of lavender flowers makes one pound of lavender essential oil). Oils produced with the aid of chemical solvents are not considered true essential oils because the solvents may change the oils’ fragrance or cause skin irritation. Each essential oil has a different chemical makeup that affects how it smells, is absorbed, and affects the body. Essential oil aroma fades quickly when exposed to the air.

Essential oils are used individually or in blends. They are most often inhaled, either directly by floating drops on hot water in an inhaler, or indirectly using a room diffuser. Essential oils also may be applied in a diluted form into a carrier oil and massaged into the skin or mixed with lotions or bath salts, and can also be found in a broad range of personal care products.

Many essential oils are used in aromatherapy, including those from Roman chamomile, geranium, lavender, tea tree, lemon, ginger, cedarwood, and bergamot. Most essential oils have been classified as “generally recognized as safe” (GRAS) at specified concentration limits by the U.S. Food and Drug Administration (FDA). The FDA includes approximately 160 essential oils, solvent-free oleoresins (a mixture of essential oils and a resin), and natural extractives (including distillates) that are GRAS for their intended use. However, aromatherapy products do not need approval by the FDA.

Aromatherapy is used or claimed to be useful for a vast array of symptoms and conditions—from sedation to arousal, kidney failure to Parkinson's disease, psychiatric disorders to labor pain.

Training and certification in aromatherapy are available at several schools in the United States. There are no professional standards for aromatherapists, and no license is required to practice aromatherapy, nor is there standardization of the treatments used for specific conditions; treatment is dependent on the health condition and the training and experience of the individual aromatherapist. This lack of standardization has, in part, resulted in variability of the research on the effectiveness of aromatherapy.

The National Association for Holistic Aromatherapy (NAHA) and the Alliance of International Aromatherapists are the two governing bodies for national educational standards for aromatherapists. NAHA is taking steps toward standardizing aromatherapy certification in the United States and approves the aromatherapy certificate programs of many of the schools.

What the Research Says about Aromatherapy

There is no evidence-based research showing that aromatherapy or the use of essential oils can treat any serious physical or mental health condition. Nevertheless, many studies suggest that they may have therapeutic applications. It is important to remember that even those studies supporting the benefits of aromatherapy are not yet supported by clinical trials. Prior to the 1990’s, there was little aromatherapy research conducted in English-speaking countries. There is much work to be done before aromatherapy and essential oils are considered a replacement for or an alternative to conventional medicine. The growing interest in natural therapies and increasing demand for effective, safe, natural products will continue to drive additional research supporting the use of essential oils.

At the same time, the National Cancer Institute reports that safety testing on essential oils has found very few side effects, although swallowing large amounts of essential oils is not recommended. Essential oils may cause allergic reactions and irritation if in contact with the skin for extended periods of time, and may result in sun sensitivity, especially after topical use of citrus oils.

For many years, parents have been told that lavender and tea tree essential oils can cause endocrine disruption in children, specifically prepubertal gynecomastia (enlarged breasts) in boys and other hormonal disorders in children, despite a lack of scientific evidence supporting these claims. In a study published in the International Journal of Pediatrics and Adolescent Medicine of more than 550 children aged 2–15 years old, researchers confirmed that there is no evidence of a relationship between the use of lavender or tea tree essential oils and endocrine disruption in children.

The Natural Medicines database lists several “possibly effective” uses for aromatherapy and essential oils to treat:

• Anxiety
• Menstrual cramps
• Labor pain
• Premenstrual syndrome (PMS)
• Anxiety before surgery
• Stress

The database points out that it is generally unclear which essential oils or blends work best, and whether more than one essential oil will achieve the same benefit.

The Natural Medicines database also identifies that aromatherapy and essential oils are “possibly ineffective” for pain in people with cancer, and “possibly ineffective” for labor duration, contractions, and the need for a C-section during childbirth.

Aromatherapy is used or claimed to be useful for a vast array of symptoms and conditions – from sedation to arousal, kidney failure to Parkinson's disease, psychiatric disorders to labor pain. The evidence-based research on aromatherapy and essential oils is growing, but there are challenges and limitations. Some of the studies are only observational or performed in the laboratory rather than on human patients following clinical trial protocols.

Some of the more common uses of aromatherapy and essential oils include treatment of stress, anxiety, depression, nausea, and sleep quality, as well as antibacterial and anti-inflammatory agents.

Common Uses

Some of the more common uses of aromatherapy and essential oils include treatment of stress, anxiety, depression, nausea, and sleep quality, as well as antibacterial and anti-inflammatory agents.

Stress, Anxiety, and Depression

Human trials have investigated aromatherapy in the treatment of stress, anxiety, and depression in patients with critical illnesses or in other hospitalized patients. In an Iranian study published in Nepro-Urology Monthly of 46 hemodialysis patients, researchers found the inhalation of rose water improved the patient’s emotional and spiritual condition during treatment. In an analysis of five German double-blinded and randomized controlled trials of patients with moderate to severe anxiety, the use of lavender oil was found to be effective in reducing that anxiety.

In a controlled trial with 103 cancer patients in a palliative care setting, participants were randomly assigned to receive massage (control group) or massage with Roman chamomile essential oil (aromatherapy massage group). After two weeks, there was a statistically significant reduction in anxiety in the aromatherapy massage group and improvement in symptoms, including improvements in psychological, quality of life, severe physical, and severe psychological scores. The control group also showed improvement, but such improvements were not statistically significant.

In a study of 58 mostly breast cancer patients that completed six aromatherapy sessions at a UK regional cancer center, researchers found significant improvements in anxiety and depression as compared to the patients’ anxiety and depression measurement before the six sessions.

However, not all the studies have supported the benefits of aromatherapy. A placebo-controlled, double-blind, randomized trial with 313 patients receiving radiation therapy was conducted in Australia. The patients were randomly assigned to one of three groups (carrier oil with essential oils; pure essential oils of lavender, bergamot, and cedarwood; or carrier oil only), and received their oils by inhalation. Researchers found there were no significant differences reported in depression or psychological effects between the groups. The group that received only carrier oil showed a statistically significant decrease in anxiety as compared with the two groups receiving essential oils.

A study of aromatherapy using two contrasting scents, lemon and lavender, in people under stress found that lemon had a positive effect on mood but neither scent affected stress indicators, biochemical markers of immune system changes, or pain control.

Nausea

A UK study found that aroma sticks with oils like lavender, lemon, frankincense, bergamot, orange sweet, and peppermint were effective in alleviating nausea and encouraging relaxation among cancer patients.

A randomized, controlled investigation of the effects of inhaled ginger essential oil on alleviating chemotherapy-induced nausea and vomiting of breast cancer patients was conducted in Malaysia. Researchers noted significant reductions in nausea after inhalation, but the effect was not sustained for the entire chemotherapy treatment. The inhaled ginger had limited effects on vomiting.

However, an evaluation of the effectiveness of orange essential oil for the reduction of nausea, retching, and/or coughing by patients receiving stem cells found that sniffing sliced oranges was more effective than the essential oil.

Sleep Quality

Research has been conducted in recent years examining the use of essential oils and aromatherapy to aid sleep issues. A meta-analysis of 12 Korean studies revealed that aromatherapy was effective in improving sleep quality. The authors noted that it is essential to develop specific guidelines for the efficient use of aromatherapy.

A randomized trial was conducted with 50 newly diagnosed patients with acute leukemia receiving intensive induction chemotherapy. The patients were offered a choice of three essential oil scents: lavender, peppermint, or chamomile. They received either the chosen aromatherapy or a placebo every other week for three weeks. Researcher found that aromatherapy improved insomnia and other sleep symptoms experienced by the patients. Improvements were noted in tiredness, drowsiness, lack of appetite, depression, anxiety, and well-being.

In a study designed to compare the effects of four-week courses of aromatherapy massage with lavender oil and massage alone on 42 patients with advanced cancer, researchers found that while there were no significant long-term benefits of aromatherapy or massage in pain control, quality of life, or anxiety, sleep scores of both groups improved significantly as compared to the control group.

There is little downside to experimenting with aromatherapy if you are looking to alleviate anxiety, stress, insomnia, or other well-being issues.

Antibacterial and Anti-Inflammatory Agents

Laboratory studies have focused on the antibacterial and anti-inflammatory effects from the topical application of aromatic oils.

In an Australian laboratory study published in the Journal of Applied Microbiology, 52 plant oils and extracts were investigated for activity against 10 different bacterial and fungal micro-organisms including Candida albicans (thrush), Escherichia coli (e. Coli), Salmonella enterica subsp. enterica serotype typhimurium (salmonella), and Staphylococcus aureus (staph). Lemongrass, oregano, and bay inhibited all the organisms tested, and rosewood, coriander, palmarosa, tea tree, niaouli, peppermint, spearmint, sage, and marjoram inhibited all the organisms except Pseudomonas aeruginosa (a bacteria that can cause infection found mostly in hospital settings). The other oils and extracts had either limited or no impact on the microorganisms evaluated. The study confirmed that many essential oils and plant extracts possess in vitro antibacterial and antifungal activity.

A 2010 study in the Journal of Lipid Research suggested that essential oils can reduce inflammation. The laboratory study found that six essential oils (thyme, clove, rose, eucalyptus, fennel, and bergamot) had anti-inflammatory properties and that thyme was most effective.

While the lab studies are promising, the results in human clinical trials are mixed.

In one successful human study, a randomized double-blind clinical trial was conducted with 60 patients over a 45-day period who had mild to moderate acne. Researchers found the group that used 5% tea tree oil-based gel showed improvement in the severity of their acne compared to the control group because of the anti-inflammatory and antimicrobial properties of the tea tree oil.

There is little downside to experimenting with aromatherapy if you are looking to alleviate anxiety, stress, insomnia, or other well-being issues. Work with an aromatherapist to find the essential oils or oil blends that work best for you. Before turning to aromatherapy for more serious health concerns, keep an eye on developing research in this area.

For additional information on the use of essential oils, check out The Healing Power of Essential Oils, a webcast hosted by KnoWEwell's Chief Health Officer, Dr. Tom O'Bryan. For a description and registration link to replay the webcast, click here.