Cineole

PhytochemicalTerpene

What is it

Cineole, also called 1,8-cineole or eucalyptol, is a monoterpene oxide that is the principal aromatic compound in eucalyptus oil and a major component of rosemary, sage, and other essential oils.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Acute bronchitis and sinusitis (pharmaceutical cineole)

Good Evidence

Randomized trials of pharmaceutical-grade cineole (200 mg three times daily) show reductions in symptoms and frequency of acute bronchitis and sinusitis episodes.

Asthma symptom management (pharmaceutical cineole)

Limited Evidence

Small trials suggest cineole may reduce oral steroid requirements in some patients with steroid-dependent asthma; evidence is limited.

How it works

Cineole has mucoactive and anti-inflammatory effects in the respiratory tract, reducing cytokine production and supporting mucus clearance. Pharmacological studies show modulation of TNF-alpha and leukotriene production. In Europe, cineole is approved as a medical product for bronchitis and sinusitis.

Dosage

European clinical studies of pharmaceutical-grade cineole (Soledum, Myrtol) have used 200-600 mg/day in capsules for respiratory indications. Supplement labels vary in concentration.

When and how to take it

Often taken with or after meals to reduce gastrointestinal upset. Capsules may be enteric-coated.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Pharmaceutical cineole (enteric-coated capsule)

Most studied form in clinical research.

Designed for release in the small intestine to reduce gastrointestinal upset

Essential oil (eucalyptus, rosemary)

For aromatic or topical use; not for unmonitored ingestion.

Highly concentrated; use diluted only

Safety

Cineole is generally well tolerated at typical doses. Gastrointestinal upset, allergic skin reactions, and (rarely) bronchospasm have been reported. Concentrated eucalyptus oil can be toxic if ingested undiluted, especially in children.

Who should be cautious

Avoid in pregnancy, breastfeeding, and in children under 6. Anyone with asthma should test for bronchospasm sensitivity before regular use. Never ingest undiluted essential oils.

Interactions

Cineole induces cytochrome P450 enzymes, potentially reducing levels of drugs metabolized by CYP3A4. Discuss with a clinician if you take prescription medications.

Food sources

Eucalyptus leaves (tea)

Amount
variable
%DV
—

Rosemary and sage (culinary)

Amount
trace amounts
%DV
—

Frequently asked questions

Is cineole the same as eucalyptus oil?⌄

Cineole is the main active component of eucalyptus oil but is also extracted as a standardized pharmaceutical for respiratory conditions.

Can I ingest eucalyptus oil directly?⌄

No. Undiluted essential oil can be toxic. Use pharmaceutical capsules or commercially available diluted preparations instead.

References

Cineole on Wikidata — Wikidata link

Cineole (ChEBI:27961) — ChEBI link

Cineole on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Cineole (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.