Phytotherapy · Respiratory & Antiseptic Support · Myrtaceae

Eucalyptus

Eucalyptus globulus Labill. (Myrtaceae) — the tall blue gum of southern Australia and Tasmania, whose leaf oil is 70 to 75% 1,8-cineole. Cineole has been tested in placebo-controlled trials in COPD and asthma, while the essential oil itself carries real toxicity risks when swallowed.

40 Primary Refs
12 Properties
Leaf Parts Used
✦ Researched
Last Updated October 25, 2026
Primary Source Wikiphyto · NCBI PubMed · COPD Trial
Family Myrtaceae
Tall Evergreen Tree · Southern Australia

Botanical Overview

Eucalyptus globulus is a large ornamental tree from southern Australia and Tasmania, cultivated in warm temperate countries such as Spain, Portugal and Australia. Its bark is smooth and greyish; young branches bear opposite, oval leaves, while older branches carry alternate, sickle-shaped, leathery ones. The flowers' stamens are covered by a lid, which gives the genus its Greek name (eu “well”, kaluptos “covered”).

HabitTree, ~30 m
Max HeightUp to 100 m (Australia)
BarkSmooth, greyish
LeavesTwo forms
Taxonomic Classification

Taxonomy & Identification

Latin Name
Eucalyptus globulus Labill.
Family
Myrtaceae
Common Names
Eucalyptus, Blue Gum, Tasmanian Blue Gum, Eucalyptus globuleux
Parts Used
Leaf of the older branches; essential oil of the leaves
Botanical Authority
Labillardière, who found it in 1800 on a voyage to Australia
Regulatory Status
French Pharmacopoeia, list A (leaf)
Ethnobotany & Traditional Use

History & Tradition

Eucalyptus was reputed to purify marshy areas, and its planting is said to have helped drive malaria out of Italy and southern France.

In the countries where it grows, the leaves are used as an antiseptic of the sinuses, the nasopharynx and the lungs. The species name honors Labillardière, who discovered the tree in 1800 on a voyage to Australia.

Modern research has centered on 1,8-cineole in COPD and asthma, and on the antimicrobial activity of the essential oil. 363710

⚠ Trials Used Pure Cineole

The COPD and asthma trials tested 1,8-cineole (eucalyptol) as an add-on to usual treatment, not whole eucalyptus oil, so their results apply to cineole preparations. 3637

Timeline

Discovered by Labillardière

1800

Found during a voyage to Australia and named in his honor.

Marsh Sanitation

Traditional Belief

Planting is said to have pushed malaria back in Italy and southern France.

Respiratory Antiseptic

Traditional Use

The leaves serve as an antiseptic of the sinuses, nasopharynx and lungs.

Cineole Trials

2009 – 2012

Placebo-controlled trials in COPD and asthma.

The Key Compounds

1,8-Cineole — Deep Dive

The terpene oxide that dominates eucalyptus oil, and the compounds that accompany it.

🧪

1,8-Cineole (Eucalyptol, 70–75%)

With mucolytic, bronchodilating and anti-inflammatory effects, cineole reduced COPD exacerbations and improved respiratory function and dyspnea in asthma. 3637

🧬

Aromadendrene

A sesquiterpene that acts synergistically with 1,8-cineole against antibiotic-susceptible and antibiotic-resistant pathogens. 15

🌲

α-Pinene & Other Monoterpenes

α-Pinene (10–12%), limonene, γ-terpinene and p-cymene complete the oil. Globulol and ledol are the sesquiterpenols.

🍃

Flavonoids & Jensenone

The foliar oil glands are a rich source of flavonoids such as pinocembrin, alongside the monoterpene ketone jensenone. 2

Pharmaceutical Preparations

Parts Used & Available Forms

The leaf of the older branches and its essential oil are used, in three documented forms.

Leaf

The sickle-shaped leaves of the older branches, listed in the French Pharmacopoeia (list A).

Leaf

Mother Tincture

Teinture-mère of the leaves.

Liquid Extract

Essential Oil

Distilled from the leaves; swallowing it undiluted is dangerous.

Essential Oil

Clinical Dosimetry

Dosages

Doses are given for the essential oil and for 1,8-cineole; the source page advises caution and short courses.

Form Dose Frequency Context Notes
Essential Oil (Commission E) 0.3–0.6 g (240–480 mg of 1,8-cineole) Per day Respiratory conditions German Commission E reference. 1
Essential Oil (Caution Limits) Under 300 mg 150–300 mg: up to 2 weeks; under 150 mg: up to 1 month Safety limits About 75 mg of 1,8-cineole per day appears safe.
1,8-Cineole (Trials) 200 mg For 6 months, with usual treatment Asthma Double-blind trial of 247 patients. 37
Suppositories & Oral Drops Not specified Not specified Adults and children over 30 months (suppositories) Oral drops are combined with other essential oils.
Phytochemistry

Composition

Leaf constituents and the profile of the essential oil; no gemmotherapy (bud) fraction is documented for eucalyptus.

Leaf — Primary Constituents

Essential OilRich in 1,8-cineole (eucalyptol), 70–75%
Major
FlavonoidsNumerous, including pinocembrin 2
Present
TanninsPresent in the leaf
Present
β-TriketonesPresent in the leaf
Present

Essential Oil Profile

Terpene Oxide1,8-Cineole, 70–75%
Major
Monoterpenesα-Pinene (10–12%), limonene, γ-terpinene and p-cymene
Present
SesquiterpenesAromadendrene; sesquiterpenols globulol and ledol
Present
Monoterpene KetoneJensenone
Present

Plant Properties — Pharmacodynamics

Twelve pharmacodynamic properties are documented for eucalyptus, with randomized trials of cineole in COPD and asthma.

12 Properties Respiratory Antimicrobial Clinical Trials
🫁

Antitussive, Expectorant & Mucolytic

The leaf is a respiratory antiseptic, expectorant and decongestant, and the oil is antitussive, expectorant and mucolytic, with a marked bronchopulmonary affinity. 10

🌬️

Respiratory Function

In asthma, cineole at 3 × 200 mg/day for 3 days inhibited production of LTB4 and PGE2 by monocytes and improved respiratory tests. 5

🔥

Anti-Inflammatory & Analgesic

The extract inhibits nitric oxide, and the essential oil shows analgesic and anti-inflammatory effects. 62930

🦠

Antibacterial

Active against E. coli and S. aureus, including multidrug-resistant strains. 1112

💊

Resistant Strains & Biofilm

Active against MRSA and vancomycin-resistant enterococci, against Proteus mirabilis biofilm, and, by quorum-sensing inhibition, against M. tuberculosis and Acinetobacter baumannii. 13141516

🍄

Antifungal

Active against Candida and against Trichosporon ovoides scalp infection (in combination with other oils). 341727

🧬

Antiviral

Active against several viruses, including herpes simplex and influenza, through hemagglutinin inhibition or by air filter and aerosol. 172223242526

🛡️

Immunostimulant

Strengthens innate immunity and the humoral response in poultry studies. 2021

🩹

Wound Odor Reduction

Reduced the smell of malodorous necrotic cancer wounds, alone or blended with tea-tree and grapefruit oils. 1819

✨

Antioxidant

The essential oil shows antioxidant and cytotoxic effects in laboratory assays. 28

📉

Antidiabetic

Reduces postprandial hyperglycemia and hyperfructosemia, and phenolic compounds inhibit enzymes involved in type 2 diabetes. 789

🪲

Insecticidal

Effective against fleas and lice (including permethrin-resistant lice), and Myrtaceae oils are insecticidal against Tribolium beetles. 31323334

Clinical Applications

Clinical Indications

Eucalyptus is primarily a respiratory remedy, with its best evidence in COPD and asthma.

🫁
Bronchitis, COPD & Asthma
Primary Indication
  • COPD: a systematic review and meta-analysis of herbal medicines in COPD supports this indication, and cineole added to usual therapy reduced exacerbations in a placebo-controlled, double-blind trial. 3536
  • Asthma: cineole improved lung function and reduced dyspnea in a double-blind trial of 247 patients. 37
  • Bronchitis & Cough: traditional indications of the whole plant and the essential oil.
👃
ENT & Influenza
Traditional Indication
  • Throat & Nose: pharyngitis, laryngitis and rhinitis.
  • Ears: otitis.
  • Influenza: laboratory work shows anti-influenza activity through hemagglutinin inhibition and in air-disinfection systems. 2526
🩹
Wounds & Skin Parasites
Clinical & Traditional Indication
  • Malodorous Cancer Wounds: the oil reduced the smell of necrotic tumor wounds in clinical observations. 1819
  • Fleas & Lice: a local repellent, with activity against permethrin-resistant head lice. 3132
🌿
Traditional Antiseptic Use
Traditional Indication
  • Respiratory Antiseptic: leaves used as an antiseptic of the sinuses, nasopharynx and lungs.
  • Marsh Sanitation: credited with helping to drive malaria from marshy areas.
Pharmacodynamics

Mode of Action

The source describes effects rather than a single mechanism; the following are the actions documented for cineole and the oil.

🫁

Mucolytic, Bronchodilating & Anti-Inflammatory Cineole

1,8-Cineole acts through mucolytic, bronchodilating and anti-inflammatory effects, which reduce COPD exacerbations. 36

🧪

Arachidonic Acid Metabolism

In asthma, cineole inhibited production of LTB4 and PGE2 and altered monocyte function ex vivo. 5

🔥

Nitric Oxide Inhibition

The extract inhibited nitric oxide in murine macrophages, with antiradical effects, supporting its anti-inflammatory action. 6

💊

Terpenoid Synergy & Quorum Sensing

Aromadendrene and 1,8-cineole act synergistically on resistant pathogens, and the oil inhibits quorum sensing in M. tuberculosis and A. baumannii. 1516

🧬

Hemagglutinin Inhibition

The anti-influenza effect operates by inhibiting hemagglutinin, as well as by inactivating airborne virus. 2526

Clinical Safety

Safety & Interactions

The leaf is generally well tolerated, but the essential oil is dangerous when swallowed, especially by children.

⚠ Genuine, Serious Risks Specific to the Essential Oil

Read Before Using Eucalyptus Essential Oil

  • Swallowing: about 1 mL of essential oil causes convulsions in humans, and the EMA gives a lethal adult dose of 4 to 5 mL. 38
  • Children: pure oil by mouth is discouraged; it can lower consciousness and cause seizures at high doses, although its toxicity may be overestimated. 3940
  • Infants: inhalation can close the glottis, as with menthol and camphor.
  • The leaf itself: poisoning is very unlikely, since more than 100 g would be needed.
⚠️

Adverse Effects & Precautions

  • General Tolerance: good; mild and rare effects include heartburn, nausea, vomiting and diarrhea.
  • Oral Essential Oil: may cause a general reaction, with shock, a fall in blood pressure and a rapid pulse.
  • Inhalation: can irritate the nasal mucosa.
  • Topical Use: an allergic skin reaction is possible.
🚫

Contraindications & Interactions

  • Pregnancy: avoid.
  • Drug Interactions: rare.
  • Dose Limits: keep to the doses and durations given in the Dosages section.
  • Regulatory Status: French Pharmacopoeia, list A (leaf).
Clinical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Consult a qualified healthcare provider before using eucalyptus essential oil, particularly in pregnancy, in infants and children, or at any dose above those described here.
Common Questions

Frequently Asked Questions

What is eucalyptus used for?
Eucalyptus leaf and its essential oil are used for respiratory conditions: bronchitis, cough, asthma, COPD, sore throat, laryngitis, colds and influenza, rhinitis and otitis. The essential oil is also a local repellent against fleas and lice.
Does eucalyptus help with COPD and asthma?
Two placebo-controlled, double-blind trials tested 1,8-cineole (eucalyptol), the main compound of eucalyptus oil, as an add-on to usual treatment: it reduced exacerbations in COPD and improved lung function and dyspnea in asthma. The trials used cineole, not whole eucalyptus oil.
What is 1,8-cineole?
1,8-Cineole, also called eucalyptol, is a terpene oxide that makes up 70 to 75% of eucalyptus globulus essential oil. Its mucolytic, bronchodilating and anti-inflammatory effects explain most of the respiratory use of the plant.
What is the usual eucalyptus oil dosage?
The German Commission E gives 0.3 to 0.6 g of essential oil per day, equal to 240 to 480 mg of 1,8-cineole. The source page advises staying under 300 mg of essential oil, limiting 150 to 300 mg to 2 weeks and under 150 mg to 1 month.
Is eucalyptus oil toxic if swallowed?
Yes. About 1 mL of essential oil swallowed can cause convulsions in humans, and the EMA gives a lethal adult dose of 4 to 5 mL. Poisoning from the leaf itself is very unlikely, since more than 100 g would be needed.
Is eucalyptus safe for children?
Pure essential oil by mouth is discouraged in children because it can reduce consciousness and cause seizures at high doses, although its toxicity may be overestimated. Inhalation can irritate the nose and, in infants, cause the glottis to close, as menthol and camphor do.
Can pregnant women use eucalyptus?
Eucalyptus is to be avoided during pregnancy. Drug interactions are rare.
Is eucalyptus antibacterial or antiviral?
In laboratory studies eucalyptus essential oil is antibacterial against E. coli and S. aureus, including multidrug-resistant strains such as MRSA, and antiviral against several viruses including influenza and herpes simplex. These are mostly in vitro results.
Can eucalyptus lower blood sugar?
Eucalyptus leaf extract lowered blood glucose in mice and reduced the rise in fructose after sucrose in rats, and its phenolic compounds inhibited several enzymes involved in type 2 diabetes in vitro. These are animal and laboratory findings only.
Sources

Bibliography

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Additional Sources

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Schnitzler P, Schön K, Reichling J. Antiviral activity of Australian tea tree oil and eucalyptus oil against herpes simplex virus in cell culture. Pharmazie. 2001;56:343–347.
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ESCOP. Eucalypti aetheroleum. ESCOP Monographs. 2nd ed. Georg Thieme. 2003:150–156.