Essential Oil Inhalation and Acute Stress Response in Healthy Adults

Essential oils and essential oil blends are widely used in non-clinical settings; however, objective data describing short-term physiological and subjective responses to inhalation under controlled experimental conditions remain limited. This study is designed to evaluate acute autonomic and self-reported responses to essential oil inhalation during standardized laboratory procedures involving psychosocial stress and guided relaxation.

This is a randomized, double-blind, placebo-controlled, parallel-group study conducted in healthy adults aged 18-45 years. Participants are assigned to inhale either an essential oil (or essential oil blend) or a placebo comparator administered via an identical aroma stick. Inhalation occurs at standardized time points during two study visits.

During Study Visit 1, participants undergo the Trier Social Stress Test - Group version (TSST-G), a validated laboratory paradigm designed to induce temporary psychosocial stress through public speaking and mental arithmetic tasks performed under observation. Inhalation occurs during baseline, preparation, stress, and recovery phases. During Study Visit 2, participants undergo a structured guided meditation session under controlled environmental conditions, with inhalation occurring at standardized intervals.

Physiological measures are collected continuously using a wrist-worn wearable device capable of measuring heart rate, heart rate variability (HRV), and electrodermal activity (EDA). Subjective responses are assessed using validated instruments including visual analog scales for stress and calm, PROMIS Anxiety, GAD-7, and PANAS. The primary outcome is change in stress response as measured by area under the curve (AUC) for visual analog scale stress scores across the stress and recovery period.

The study employs an adaptive design with an initial planned enrollment of 100 participants (50 per arm) and a prespecified interim analysis for potential expansion to a maximum of 200 participants. Statistical analyses include comparison of stress and physiological responses between groups using baseline-adjusted models.

This study is exploratory in nature and is intended to characterize acute responses associated with essential oil inhalation under controlled conditions. It is not designed to diagnose, treat, mitigate, or prevent any disease or medical condition.

Inclusion criteria

Age 18-45 years, inclusive

Able to read, write, and understand English

Willing and able to provide informed consent

Willing to attend two in-person study visits

Generally healthy, as determined by medical history and screening review

Exclusion criteria

Known asthma, chronic obstructive pulmonary disease (COPD), significant lung disease, heart disease, or other medical condition that may compromise safety or data integrity

Pregnancy or pregnancy within the past 90 days

Known allergy or sensitivity to essential oils or study placebo materials

Current smoking, vaping, chewing tobacco, or use of recreational drugs

Regular use of essential oils applicable to the study phase (>3 times per week for ≥2 weeks within the past month) without a minimum 1-month washout

Unwillingness to abstain from alcohol for at least 72 hours prior to each study visit

Failure to meet inclusion criteria