Pressed peel oil of an Italian citrus fruit, inhaled for calm or applied diluted to skin. The clearest signal is short-term: breathing the aroma lowers reported anxiety within minutes, from many small brief studies. Mood, sleep, pain and dementia claims rest on thinner ground. One well-characterized hazard: light-activated skin burns, avoidable with care about sun exposure. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Salivary cortisol, waking and evening | Waking 0.30–0.75 µg/dL; evening below 0.10 µg/dL | Direct readout of the stress axis the oil is claimed to damp |
| Heart rate variability, overnight RMSSD | No established target; a rise of 10% or more from the individual's own 7-day baseline | The parasympathetic index that moved in the bergamot vapour trial |
| Resting blood pressure | 110–120 / 70–78 mmHg | Fell alongside heart rate in the schoolteacher aromatherapy study |
| Resting heart rate | 55–65 bpm | Simplest bedside marker of the autonomic shift |
| Pittsburgh Sleep Quality Index | Total score below 5 | The instrument that detected the sleep effect in the postmenopausal trial |
| State-Trait Anxiety Inventory, state form | Score below 40 | The primary endpoint in the pre-surgical bergamot trial |
| Photopatch or repeat open application test | Negative reading at day 3–4 | Detects phototoxic and oxidized-terpene allergic reactivity before routine use |
| Trough level of any narrow-therapeutic-index CYP3A4 substrate | Within the drug's established therapeutic reference range | Detects the furanocoumarin interaction if the oil is ingested |
Cadence: Baseline over two weeks before starting; subjective ratings weekly for the first month, then monthly; cortisol and heart rate variability at 4 weeks, then every 3–6 months while topical or daily inhaled use continues; treated skin inspected after the first three sun exposures; whole protocol reassessed every 6–12 months.