Lemon oil may lift your mood, but aromatherapy is no better than distilled water in relieving pain, healing wounds, boosting immune function, or easing stress. Those are the key findings of a rigorous investigation into the purported benefits of this scent-based approach to health and wellness. The study, conducted by researchers in behavioral medicine at Ohio State University, examined the effects of the two most studied odors — lemon oil (promoted as a stimulant) and lavender oil (promoted as a relaxant) — on various physiological systems that influence health. Results were published in the April 2008 issue of the journal Psychoneuroendocrinology.
Aromatic plant oils have been used since ancient times to improve mood and health. Today, such oils, also known as essential oils, are incorporated in massage, added to baths, or inhaled in steam or through a diffuser. Little systematic empirical research has been devoted to aromatherapy, and many of the available studies are inadequate. The Ohio State study is particularly well designed and should set a standard for future research on the health effects of aromatherapy.
Researchers monitored the blood pressure and heart rate of 56 healthy volunteers who wore cotton balls infused with lemon, lavender, or distilled water (placebo) taped under their noses. Half the group were told which scent they’d be exposed to and what to expect — for example, that lavender has a calming effect and might lower heart rate or provoke warm memories. The other half were told only that they would be sniffing various floral and fruit scents.
Emotional responses and mood were evaluated by questionnaires before and during the sessions. Wound healing was tested by the application and removal of a tape on the skin, and reactions to pain were assessed by having subjects plunge their feet into freezing water. Blood and saliva samples were taken throughout to measure changes in endocrine and immune function. Among the findings: lemon oil enhanced mood, but lavender did not. Levels of the stress hormone norepinephrine remained elevated after the ice-water test when subjects smelled lemon rather than lavender or water. And both lemon and lavender delayed immune responses in a skin reactivity test more than distilled water did. This last finding is particularly relevant because aromatherapy is often promoted as a way to boost immune function. The bottom line: lemon clearly lifted mood, but neither lemon nor lavender oil enhanced physical well-being. Expectations had little influence on outcomes.
The negative findings from this one study aren’t likely to dampen enthusiasm for aromatherapy; many people say the practice simply makes them feel good. And some solid research suggests that aromatherapy has value. For example, a systematic review of randomized controlled trials published in 2000 found that aromatherapy massage was helpful as part of supportive care in a hospital setting, particularly in reducing anxiety. A 2007 study in the journal Obesity Surgery reported that surgical patients treated with lavender oil (applied through an oxygen face mask) required half as much postoperative pain medication as patients who received unscented oil. Finally, according to the independent Natural Medicines Comprehensive Database, there’s some evidence that topical applications of certain essential oil combinations can help treat alopecia areata (hair loss).