Material guide: 1,8-cineole — the shortest longevity in the series, and the only material here that is also a prescription drug

The longevity record in the database for this one reads:

4 hours at 100%

Four hours, neat. That is the shortest number across sixty material guides — cyclamen aldehyde last time was 72 hours, and omega-pentadecalactone before that was 400.

And its vapour pressure is 1.9 mmHg, the highest in the series.

Those two facts are the same fact. We measured vapour pressure against longevity across 1,319 materials and got a log-log correlation of −0.625, with quartile landmarks at 1.163 mmHg → 4 hours. Cineole sits right at the start of that line, almost too neatly for an example.

The short version

• Four hours, 1.9 mmHg. The fastest-evaporating, shortest-lasting material in the series, with the two numbers confirming each other.
• It is also a drug. Marketed in Germany as a 200 mg capsule for respiratory use. That is rare for something on a perfumer's shelf.
• A 2024 trial of 522 people reports a 38% reduction in disease burden with early dosing — in a study that was open-label and non-randomised, and where all seven authors received financial support from the manufacturer or its group. Both halves belong in the same sentence.
• There are two paediatric case reports, and one of them is topical. A six-year-old developed slurred speech, ataxia and muscle weakness progressing to unconsciousness after widespread application of a home remedy containing eucalyptus oil.
• The database's GHS field is empty, while the toxicity field records convulsions and effects on seizure threshold. An empty field is not a clean bill of health — we have been caught by this before.
• Flash point 50 °C, the lowest in the series. Store it as a genuinely flammable liquid.

The basics

Also known as	Eucalyptol
CAS	470-82-6
Formula	C₁₀H₁₈O
Molecular weight	154.25
Type	Natural/synthetic
Odour	Eucalyptus, herbal, camphoreous, medicinal
Odour family	herbal
Strength	High (evaluate at 10% or below)
Longevity	4 hours at 100% (a neat value)
Appearance	Colourless clear liquid
Boiling point	176–177 °C @ 760 mmHg
Melting point	1–2 °C
Flash point	50 °C
Vapour pressure	1.9 mmHg @ 25 °C
logP	2.50 (est)
Regulatory	JECFA, FEMA GRAS, CoE, FLAVIS
Suppliers	77
Corpus position	eucalyptol in 24 formulas (median 1.75%) plus eucalyptus oil in 12 (median 1.52%)

It is a molecule; eucalyptus oil is a mixture

Worth settling first, because it will make you buy the wrong thing.

The eucalyptus globulus article opens on exactly this: eucalyptus oil is not another name for cineole. It is a natural mixture whose proportions shift with origin, leaf age and plant part — in a 1995 study of leaf oils, 1,8-cineole ranged from 4.10% to 50.30%, while the European Pharmacopoeia specification for medicinal eucalyptus oil requires at least 70%.

This article is about the pure molecule.

The corpus keeps them separate too: eucalyptol in 24 formulas, eucalyptus oil in 12. That mirrors the four names of omega-pentadecalactone — there, one molecule split across four names; here, two names pointing at different things. Both will corrupt a count, in opposite directions.

About that four hours

Most materials in the series record longevity in the tens to hundreds of hours. This one records 4.

In context:

Material	Vapour pressure	Longevity record
1,8-cineole	1.9 mmHg	4 hours at 100%
Cyclamen aldehyde	0.009 mmHg	72 hours at 100%
Omega-pentadecalactone	—	400 hours at 10% in DPG

Three materials landing in a straight line, and it is the regression we ran: a log-log correlation of −0.625 between vapour pressure and longevity, with quartile landmarks at 1.163 mmHg → 4 hours, 0.08 → 24, 0.011 → 104, 0.001 → 216.

Cineole's 1.9 mmHg and 4 hours land in the fastest bin.

What that means at the bench: it is a top note, and a very top one. Using it to build "lasting coolness" is the wrong direction; what it does is the moment the bottle opens.

Note also that its strength is high (evaluate at 10% or below), so evaporating fast is not the same as being faint. It is loud for ten minutes and then it leaves.

It is also a drug

That is unusual enough on a perfumer's shelf to deserve its own section.

1,8-cineole is marketed in Germany as a 200 mg enteric capsule (Soledum®, CNL-1976) for inflammatory respiratory conditions. So its clinical literature is a different kind of thing from the literature on most fragrance materials.

Michalsen and colleagues published a phase IV, open-label, non-randomised exploratory clinical trial in PLoS One in 2024. The design has a clever element: because common cold symptoms generally peak within two days, enrolling people after onset is difficult, so they enrolled participants before they caught a cold. Of 522 adults enrolled, 329 developed a cold and took 200 mg cineole three times daily for up to 15 (±2) days. The primary endpoint was burden of disease on the WURSS-11 survey.

Comparing three strata by time from onset to treatment (≤12 h, >12 to ≤24 h, >24 h):

• The earliest-treated stratum had the lowest AUC-WURSS (Spearman correlation coefficient 0.36), reducing overall burden of disease by 38% (p < 0.0001);
• The symptom severity peak was earlier and lower, with shorter time to remission (average 8.9 days versus 10.7 days for the latest initiation, p < 0.05);
• Quality of life recovered higher and faster (p < 0.05);
• Tolerability was mostly rated "very good", with adverse events of suspected causal relationship in 4.3% of participants.

Now the other half.

The trial was open-label and non-randomised — no blinding, no randomised allocation, and the strata were defined by when participants chose to start taking the drug. People who dose early and people who put it off may differ in ways that have nothing to do with the drug.

And the conflict of interest statement reads: "All authors received financial support from Cassella-med GmbH & Co. KG or MCM Klosterfrau Vertriebsgesellschaft mbH, Klosterfrau Healthcare Group for the submitted work." Klosterfrau is the company that sells Soledum. Several authors separately list consulting and speaker fees from many pharmaceutical firms.

None of that makes the study fake. A journal accepted it, the design innovation of enrolling before onset is genuinely useful, and the conflicts were fully disclosed — which is what should happen. But a manufacturer-funded trial with no blinding, no randomisation, and comparisons across self-selected strata supports a smaller claim than the figure 38% sounds like.

We have written about how to read fragrance studies, and this trial is probably the best one in the series to practise on.

Two paediatric case reports

This section connects straight to the previous article on doing perfumery with children.

The topical one. Darben and colleagues, in the Australasian Journal of Dermatology in 1998, reported systemic eucalyptus oil toxicity from topical application: a six-year-old girl presented with slurred speech, ataxia and muscle weakness progressing to unconsciousness following widespread application of a home remedy for urticaria containing eucalyptus oil. Six hours after the preparation was removed her symptoms had resolved, with no long-term sequelae.

Their opening line is that eucalyptus oil's extreme toxicity on ingestion is well documented — and what they were reporting is that topical does it too.

The ingestion one. Patel and Wiggins, in Archives of Disease in Childhood in 1980, reported a three-year-old boy who accidentally ingested eucalyptus oil and developed profound central nervous system depression within 30 minutes, recovering rapidly after gastric lavage. Their closing note emphasises the extreme toxicity of eucalyptus oil.

Both are case reports, not epidemiology. A case report gives you neither an incidence rate nor a dose-response curve; the home remedy's concentration was not recorded, and the clinical context of 1980 and 1998 differs from now.

But they answer a very concrete question: "what if some gets on skin" is not theoretical for this one.

The database's toxicity field agrees: subcutaneous mouse LD50 1,070 mg/kg, with observations in the same record including spastic paralysis and convulsions or effect on seizure threshold; oral rat LD50 recorded at both 2,480 and 1,550 mg/kg from sources of different eras; dermal rabbit LD50 above 5,000 mg/kg.

The GHS field is empty, and that means nothing

Worth flagging: this record's GHS hazard statement field is blank.

Blank does not mean hazard-free. We fell into this in the naturals article: of 17,002 materials with records, only 367 carry GHS field data, which is far too little coverage to compare with.

Here, the empty GHS field sits directly beside the toxicity data above. Read both columns together.

Smelling it and using it

• Use it as a top note and expect it to leave. Four hours, 1.9 mmHg. Building lasting coolness with it is the wrong plan.
• Make a 10% stock. The strength field says high, evaluate at 10% or below. It has plenty of presence at low concentrations.
• 1.75% is the corpus median (range 0.10% to 24.00%). The top end is cool/herbal-theme formulas.
• It pushes a formula toward "medicinal". The odour field's four words are eucalyptus, herbal, camphoreous and medicinal. That medicinal quality buries delicate things easily.
• Smell it apart from menthol. Both give coolness by different mechanisms, and side by side they confuse each other.

Buying and storage

Seventy-seven suppliers, easy to get. Buy on CAS 470-82-6, and keep it distinct from eucalyptus oil.

A flash point of 50 °C is the lowest in this series, against cyclamen aldehyde's 109 °C and omega-pentadecalactone's above 104 °C. Fifty degrees means that in a hot room its vapour can form a flammable mixture, so store and ship it as a flammable liquid, away from heat and ignition sources.

It evaporates fast, so keep the bottle open briefly and cap it properly.

Regulatory and safety

Flavour listings are comprehensive (JECFA, FEMA GRAS, CoE, FLAVIS).

The database's GHS field is blank; the toxicity record is above. For use limits, check current IFRA Standards — here is how.

If your formula will be used by children, or will sit anywhere children can reach, that article's full procedure is more detailed than this section.

→ 1,8-cineole in the database: full physical data, 77 suppliers and suggested blends. → Search by odour: try "eucalyptus herbal cooling".

References

A. Michalsen et al., The impact of cineole treatment timing on common cold duration and symptoms: Non-randomized exploratory clinical trial, PLoS One, 19(1), e0296482 (2024). PMID 38236839. doi:10.1371/journal.pone.0296482

T. Darben, B. Cominos, C. T. Lee, Topical eucalyptus oil poisoning, Australasian Journal of Dermatology, 39(4), 265–267 (1998). PMID 9838728. doi:10.1111/j.1440-0960.1998.tb01488.x

S. Patel, J. Wiggins, Eucalyptus oil poisoning, Archives of Disease in Childhood, 55(5), 405–406 (1980). PMID 7436478. doi:10.1136/adc.55.5.405