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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.

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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.

How to take it

TimingThree times daily during an acute episode, as the trials did.
With food?Before meals with water; never open or crush the capsule, since the enteric coating is what stops release in the stomach.
Worth knowingOnly standardised enteric capsules at the stated dose — swallowed neat eucalyptus oil has caused seizures, particularly in children.

Frequently asked questions

Does eucalyptus oil (cineole) help sinusitis?

Cineole has moderate evidence for acute sinusitis: a placebo-controlled trial in 152 patients found 200 mg of enteric-coated 1,8-cineole three times daily improved symptoms faster, with differences visible by day four. Most cineole trials come from one product and overlapping investigators.

Does cineole help COPD?

In a placebo-controlled trial in 242 patients with COPD, add-on cineole reduced the frequency, duration and severity of exacerbations over six winter months. This is moderate evidence, largely from one manufacturer's product.

Is it safe to swallow eucalyptus oil?

No: undiluted eucalyptus oil is toxic if swallowed and has caused seizures and central nervous system depression, especially in children. Use only standardised enteric-coated cineole capsules at the stated dose, and never open or crush them.

What are the side effects of cineole capsules?

Common side effects of cineole capsules are heartburn, nausea and eucalyptus-flavoured burping. Avoid cineole in children under six, in pregnancy and breastfeeding, and with inflammatory bowel or bile duct disease; it induces CYP enzymes and may lower levels of some medications.

Scientific references

Related in Immunity

Herbal medicines: what the evidence says (335)