Moderate evidenceImmunity

Eucalyptus Oil (Cineole)

Purified 1,8-cineole (eucalyptol) in enteric-coated capsules has several placebo-controlled trials in sinusitis, bronchitis, asthma and COPD. The results are consistently positive but come largely from one product and one research group.

Evidence last reviewed: August 2026

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What the science says

Acute rhinosinusitis Moderate evidence
A double-blind randomised placebo-controlled trial in 152 patients with acute non-purulent rhinosinusitis found 200 mg cineole three times daily improved a composite symptom score faster than placebo, with differences visible by day four.
COPD exacerbations Moderate evidence
A placebo-controlled double-blind multicentre trial in 242 patients with COPD found concomitant cineole reduced the frequency, duration and severity of exacerbations over six winter months. It is one of the larger trials in this literature.
Asthma symptoms as add-on therapy Limited evidence
A placebo-controlled double-blind trial in 247 patients with asthma reported improvements in lung function and symptom scores with add-on cineole, and an earlier small trial suggested a steroid-sparing effect. Most of these trials were conducted by overlapping investigators and funded by a single manufacturer, which tempers confidence.

Dosage & safety

Studied doseThe trials used 200 mg of enteric-coated 1,8-cineole three times daily. Enteric coating matters: it prevents release in the stomach.

SafetyCommon side effects are heartburn, nausea and eucalyptus-flavoured burping. Undiluted eucalyptus oil is toxic if swallowed and has caused seizures and central nervous system depression, especially in children, so only use standardised enteric capsules at the stated dose. Avoid in children under six, in pregnancy and breastfeeding, and in people with inflammatory bowel or bile duct disease. Cineole induces CYP enzymes and may reduce the levels of some medications.

Scientific references

Therapy for acute nonpurulent rhinosinusitis with cineole: results of a double-blind, randomized, placebo-controlled trial
Kehrl W, Sonnemann U, Dethlefsen U — Laryngoscope, 2004
Concomitant therapy with Cineole (Eucalyptole) reduces exacerbations in COPD: a placebo-controlled double-blind trial
Worth H, Schacher C, Dethlefsen U — Respir Res, 2009
Patients with asthma benefit from concomitant therapy with cineole: a placebo-controlled, double-blind trial
Worth H, Dethlefsen U — J Asthma, 2012

Where to buy

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