Material guide: Eucalyptus globulus oil — one botanical name, a tenfold range inside the bottle

Catalogues often place eucalyptus oil and eucalyptol on adjacent lines, as though one were the full name and the other its shorthand. They are not. The first is a natural essential oil; the second is the single molecule 1,8-cineole. Confuse them and the odour, specification and storage decision all drift.

What matters

• “Eucalyptus globulus” gives the species, not the composition. A 1995 study spanning origin, leaf age and plant part found only 4.10–50.30% 1,8-cineole in the leaf oils. A commercial sample analysed in 2023 held 63.1%.
• European Pharmacopoeia medicinal eucalyptus oil is distilled and rectified from cineole-rich eucalyptus material and specifies at least 70% 1,8-cineole. That is a defined pharmacopoeial grade, not every perfumery oil labelled E. globulus.
• This oil is strong and fast, with a database substantivity record below four hours. It dissolves in alcohol but only slightly in water. Flash point is about 48.9 °C; keep cool, dry, protected from heat and light, and tightly closed.

Basic data

CAS	8000-48-4
Type	natural essential oil; multicomponent mixture
Botanical	Eucalyptus globulus Labill.
Odour	eucalyptus, camphoraceous, herbal, medicinal
Odour family	herbal
Strength	high (evaluate at 10% or less)
Substantivity	below 4 hours (database record)
Appearance	colourless to pale yellow clear liquid
Boiling point	about 175 °C @ 760 mmHg (mixture record)
Flash point	48.89 °C
Specific gravity	0.905–0.925 @ 25 °C
Refractive index	1.458–1.465 @ 20 °C
Water solubility	slightly soluble; 332.1 mg/L (estimated)
Other solubility	soluble in alcohol and paraffin oil
Suggested storage	24+ months; cool, dry, protected from heat and light, tightly closed
Regulatory listing	FEMA GRAS

A natural oil has no single molecular formula or molecular weight. The boiling point, flash point and solubility above are representative commercial records, not promises that every crop is identical. Use the supplier's certificate of analysis to judge a batch.

Why the same tree gives such different numbers

In 1995, Chalchat and colleagues analysed E. globulus from the Montenegro coast and eastern Spain. They sampled leaves, bare branches, flower buds and mature fruit. Depending on leaf age and origin, leaf-oil 1,8-cineole ranged from 4.10 to 50.30%; α-pinene from 0.05 to 17.85%; p-cymene from trace to 27.22%; cryptone from zero to 17.80%; and spathulenol from 0.12 to 17.00%.

Changing the plant part changed the profile again. Fruit, bud and branch oils contained 15.31%, 36.95% and 56.96% 1,8-cineole respectively. “Eucalyptus globulus oil” is therefore not a fixed recipe. Plant part, maturity, environment and processing all leave their mark on the analysis.

The sample in Čmiková and colleagues' 2023 study contained 63.1% 1,8-cineole, 7.7% p-cymene, 7.3% α-pinene and 6.9% limonene. It sits close to the cool, penetrating, medicinal eucalyptus most people recognise. It remains one sample, not a composition guarantee for the species.

Why the pharmacopoeia says 70%

The European Medicines Agency report cites the European Pharmacopoeia definition: medicinal eucalyptus oil comes from cineole-rich E. globulus, E. polybractea or E. smithii, obtained by steam distillation and rectification, and contains at least 70% 1,8-cineole.

The operative words are “rectification” and “finished specification”. The pharmacopoeia is not claiming that every leaf naturally distils above 70%. It defines which finished oil qualifies as that medicinal material. A perfumery supplier's Eucalyptus globulus may be unrectified or made to a different cineole target. The botanical name alone leaves out the decisive row.

Smelling it

• Start at 1–5%. At high strength, the cooling and medicinal facets cover the dry herb, wood and citrus-peel edges.
• Smell it beside isolated 1,8-cineole. The isolate is generally cleaner and straighter; α-pinene, p-cymene, limonene and the rest give the full oil pine, citrus or warm-wood margins.
• It opens a formula rather than finishing it. The sub-four-hour record explains why it clears the air at the top but does not support a base.
• For forest or herb effects, connect a small amount to pine, rosemary, lavender or woods. Too much quickly turns the whole formula into a cleaning-product reference.

Buying and storage

Ask for at least the botanical name, extracted plant part and 1,8-cineole content, then check whether the oil is rectified. If the use requires a pharmacopoeial grade, buy the named compliant grade with a certificate of analysis; do not infer compliance from an aroma-material label.

Soluble in alcohol does not mean ready for water. Transparent aqueous products still need a solubilisation trial. At a flash point around 48.9 °C, keep away from ignition and high heat. Store cool and dry, protected from light and tightly closed. Decant a working quantity instead of repeatedly opening a large bottle.

Regulatory and safety

Our record lists FEMA GRAS. Food listing, pharmacopoeial quality and safety in a skin formula answer three different questions; none substitutes for the others. For skin and consumer products, consult current IFRA Standards, the SDS, allergen information and rules for the finished use.

→ Eucalyptus globulus oil in the database: full properties, 129 suppliers and suggested pairings. → Search by odour: try “eucalyptus camphoraceous herbal”.

References

J. C. Chalchat et al., Chemical Composition of Eucalyptus globulus Oils from the Montenegro Coast and East Coast of Spain, Journal of Essential Oil Research, 7(2), 147–152 (1995). doi:10.1080/10412905.1995.9698489

N. Čmiková et al., Chemical Composition and Biological Activities of Eucalyptus globulus Essential Oil, Plants, 12(5), 1076 (2023). PMID 36903935. doi:10.3390/plants12051076

European Medicines Agency, Final assessment report on Eucalyptus globulus Labill., Eucalyptus polybractea R.T. Baker and/or Eucalyptus smithii R.T. Baker, aetheroleum — Revision 1 (2024).