Recent meta-analyses and systematic reviews suggest that aromatherapy is effective in treating various medical conditions, particularly those with underlying mechanisms that involve emotional and attentional information processing. Certain odors, including that of peppermint (Mentha × Piperita, Lamiaceae), may reduce pain or anxiety. The odors of other herbs, such as thyme (Thymus vulgaris, Lamiaceae), produce antibacterial antifungal, anti-inflammatory, or antioxidant effects. Many of the clinical studies, however, are of low quality. These authors discuss the conditions under which aromatherapy would be of the greatest medical value. They also introduce the aromatherapy inhaler AromaStick (AromaStick AG; Sargans, Switzerland) and discuss a series of studies of the inhaler.
The olfactory receptor genes constitute 3% of all genes. The tens of millions of olfactory receptor cells can be found in almost every organ. Because the olfactory and trigeminal systems are found in the nasal cavity; most odorant molecules stimulate both systems simultaneously, which affects the perception of odor and the somatosensory innervations associated with them.
Pointing out the various definitions of aromatherapy, the authors suggest that “a precise and narrow definition of the term defines aromatherapy as the use of scents for the purpose of provoking psychological or physiological responses.”
The effectiveness of aromatherapy depends on the following factors: the purity of the substance; the use of a single scent or complex blends; the use of natural versus synthetic scents; and the difficulty in standardizing natural plant-derived raw materials. According to the authors, effective aromatherapy should “involve natural essential oil compounds of high phytochemical quality” and “be potent enough to strongly stimulate the olfactory system without causing habituation.”
AromaStick was developed to deliver concentrated, unadulterated scents to the nose. The sniff carries the scent into the olfactory system when the inhaler is used in each nostril. According to the manufacturer’s website, six inhalers are produced as follows: Balance, Calm, Relax, Focus, Energy, and Refresh. Among the essential oils used are those of peppermint, lavender (Lavandula angustifolia, Lamiaceae), Oswego tea or beebalm (Monarda didyma, Lamiaceae), rosemary (Rosmarinus officinalis, Lamiaceae), blue gum eucalyptus (Eucalyptus globulus, Myrtaceae), and mandarin (Citrus reticulata, Rutaceae).
The inhalers have been shown to produce beneficial effects for various physiological and psychological target variables. The results of 10 studies involving a total of 465 participants and conducted by author R. Schneider are presented. The improved target variables in the studies included blood pressure, heart rate, cognitive performance, blood oxygen saturation, pain relief, and nasal symptoms. Among the participants were highly stressed participants, healthy participants, individuals with borderline hypertension, women with menstrual pain, participants with chronic back pain, and patients with seasonal rhinitis.
The findings of the studies suggest that the inhalers target various physiological systems and produce specific effects. The effects are produced only when the scents are inhaled and not when diffused in the air. According to the authors, the inhalers are more effective than other interventions intended to alter physiological processes, they enhance normal bodily and cognitive functions, and they increase effective measures when used as adjuvant therapy (for example, for pain). They are well tolerated, suitable for self-treatment, and portable. Users may vary in their response to the inhaler.
The authors acknowledge some limitations of the AromaStick studies. The exact dose of the inhaled scent cannot be controlled. Focusing mainly on whether the inhalers produce specific effects, the investigator did not examine the underlying mechanisms of the effects. Although some studies investigated symptoms over an extended period, it is unclear how long the inhaler’s effects actually last. The inhaler is successful when used regularly, which could be many times daily, and its success depends on the user’s discipline. The use of the AromaStick as an adjuvant needs further study. The effectiveness of the inhaler may differ for acute and chronic ailments. Because the study findings were not derived from a clinical setting, they may be biased.
The reported findings “across a wide range of physiological systems show that the inhalation of volatile compounds from essential oils yields almost immediate, large, and clinically relevant effects as long as the scents are delivered highly concentrated from an appropriate device. … The AromaStick® is potentially suited as a stand-alone measure to address everyday challenges or as an adjunct to medical treatments.”
Because the reported studies were funded by the AromaStick manufacturer, the principal investigator of the studies, author R. Schneider, could have been biased toward the outcomes. To prevent such bias, R. Schneider did not participate in the treatments and had no contact with the participants. All collected data were blinded as to group allocations and unblinded after the analyses. Authors N. Singer and T. Singer are co-directors of AromaStick AG.
Schneider R, Singer N, Singer T. Medical aromatherapy revisited—basic mechanisms, critique, and new development. Hum Psychopharmacol Clin Exp. 2019;34(1):e2683. doi: 10.1002/hup.2683.