Material guide: clove bud oil — twelve records under one CAS number, and bud, leaf and stem are three different products

About a 5 minute read.

Too long, didn't read

• Name: clove bud oil, CAS 8000-34-8, FEMA 2323
• 128 suppliers, 8th in the whole database by supplier count, one of the easiest natural oils to source
• Odor family spicy; descriptors: spicy, aromatic, balsamic, woody, fruity, minty, phenolic, powdery, sweet, clove, medicinal
• Longevity 188 hours @100%, strength medium
• Twelve records share this CAS, spanning three plant parts and six extraction methods
• GHS: H315 skin irritation, H319 serious eye irritation, H335 respiratory irritation. No sensitisation line
• Shelf life 24 months, specific gravity 1.038–1.060, keep sealed and away from light

One CAS number, twelve records

Start with the easiest trap. Query this database on CAS 8000-34-8 and you do not get one material, you get twelve:

Record	Suppliers	FEMA
clove bud oil	128	2323
clove leaf oil	109	2325
clove stem oil	34	2328
clove bud oleoresin	24	2324
clove bud absolute	15	none
clove bud oil CO2 extract	10	none
clove bud concrete	2	none
clove bud resinoid	2	none
clove flower oil	2	none
clove leaf oil terpeneless	2	2325
clove leaf absolute	1	none
clove leaf resinoid	1	none

The CAS number here identifies the plant, not the product. One number covers three plant parts and six extraction methods. The FEMA numbers separate them a little better, with one each for bud, leaf and stem. FEMA is not an identifier covered the problem from the other direction; this is the same point reversed. Neither is CAS.

If a supplier's quotation carries only CAS 8000-34-8, that quotation has not told you what you are buying.

Bud, leaf, stem: the three oils have different fields

	Bud oil	Leaf oil	Stem oil
FEMA	2323	2325	2328
Suppliers	128	109	34
Longevity (hr @100%)	188	116	176
Extra odor descriptors	fruity, sweet, clove	peppery	fatty
Specific gravity @25 °C	1.038–1.060	1.036–1.046	1.048–1.056
Refractive index @20 °C	1.527–1.535	1.530–1.538	1.534–1.538
FCC listed	Yes	No	No
GHS	H315 / H319 / H335	H315 / H319 / H335	(field empty)
Toxicity field	three LD50 entries	three LD50 entries	Not determined
Cosmetic uses	fragrance, perfuming	fragrance, perfuming, skin conditioning, tonic	perfuming, skin conditioning

All three open their odor field with the same four words (spicy, aromatic, woody, balsamic). The difference is what follows: bud oil adds fruity, sweet and clove, leaf oil adds peppery, stem oil adds fatty. The specific gravity ranges do not overlap, which makes that the easiest field to tell them apart in a lab.

The three longevity numbers do not fall into any intuitive order: bud 188, stem 176, leaf 116. Leaf oil, the cheapest and the one most often routed into eugenol production, has the shortest recorded longevity of the three.

The same number in the boiling point field

Bud oil and leaf oil both carry 251.00 °C @ 760 mmHg as their boiling point.

An essential oil is a mixture, and a mixture has no single boiling point. When two mixtures with different compositions carry the same boiling point, there is one explanation available: that number was not measured on either oil, it was borrowed from the major component. Neat eugenol's boiling point field reads 252–253 °C.

When two fields hold the same number measured this pattern. Read a natural oil's physical fields selectively: specific gravity and refractive index are ranges suppliers actually measured, while boiling point and water solubility carry the marks of estimation and borrowing.

Eugenol is half the oil, and its GHS entry is not the oil's

In 2021 Haro-González and colleagues at the research centre in Jalisco, Mexico, published a review of clove essential oil in Molecules (PMID 34770801), comparing how six extraction methods affect the concentration of the volatile compounds.

The composition sentence is worth copying out: eugenol is the major compound, accounting for at least 50%. The remaining 10–40% consists of eugenyl acetate, beta-caryophyllene and alpha-humulene.

Take those three back to the database:

Component	Suppliers	Longevity (hr)	First GHS line
Eugenol	97	52	Skin sensitisation Category 1, H317
Eugenyl acetate	44	400	(field empty)
beta-Caryophyllene	61	44	Acute toxicity oral Category 4, H302
alpha-Humulene	16	(empty)	(field empty)

Two things fall out of that table.

First, the whole oil outlasts its major component. Eugenol on its own records 52 hours, the oil 188. The 400 hours on eugenyl acetate is probably part of the reason. But these numbers were reported by different suppliers on their own blotters, not as one controlled set, so they are a direction rather than a measurement.

Second, and this is the one that matters: the oil has no sensitisation line while eugenol's GHS entry opens with one. Bud and leaf oil are classified H315 skin irritation, H319 serious eye irritation, H335 respiratory irritation. Irritation and sensitisation are different things. Irritation happens to anyone given enough dose; sensitisation is the immune system recognising you, and then reacting every time. An oil that is at least half eugenol shows no H317 in its own field.

GHS classification of mixtures follows its own calculation rules, and a supplier's SDS need not match a catalogue. Still, as a user, you cannot read the oil's field alone and conclude there is no sensitisation risk.

Six European clinics measured it down to 0.031%

A 2023 paper in Contact Dermatitis worked out the dose relationship for eugenol in detail (Ofenloch et al., PMID 37218587, from clinics in Heidelberg, Odense, Bari, Barcelona, Lund and Alicante).

The design: 67 subjects. First a repeated open application test (ROAT) for 21 days, twice a day, with three eugenol dilutions (2.7% down to 0.5%) plus a control. Patch testing was done before and after the ROAT, using 17 dilutions from 2.0% down to 0.00006%.

The results as reported: of the 34 subjects with contact allergy to eugenol, 21 (61.8%) had a positive patch test before the ROAT, and the lowest positive concentration was 0.031%. The ROAT was positive in 19 (55.9%), and the time until a reaction appeared was negatively associated both with the concentration applied and with the allergic reactivity established by patch testing.

The part worth remembering is the last one: in 13 subjects (38.2%) the patch test result was not reproducible, and 4 of those 13 (31.0%) still developed a positive ROAT.

A single negative patch test, in other words, does not mean no allergy. The authors concluded that eugenol can provoke a positive reaction at a very low concentration. Put 0.031% in a perfumery frame: an oil that is 50% eugenol reaches that order of magnitude at 0.062% in the formula.

Buying and storing

128 suppliers, 8th in the database, so supply is not the problem. A few practical points:

• Ask which part on the quotation. A CAS number is not enough. Bud, leaf and stem differ in price and in smell while sharing one CAS. Ask the supplier for the FEMA number or for bud/leaf/stem in writing.
• One thing you can check yourself on arrival: specific gravity. The three ranges do not overlap: 1.038–1.060 (bud), 1.036–1.046 (leaf), 1.048–1.056 (stem). That is a first pass at telling them apart without sending anything out for GC.
• Shelf life 24 months, stored cool, dry, sealed and away from heat and light. Phenolics oxidise and darken.
• Strength medium, with no recommended evaluation dilution in the database. Given where it sits in a formula, starting at 10% is a reasonable place to begin.
• For anything going on skin, check the current IFRA Standards and the EU allergen labelling rules yourself. The regulatory field reads FEMA GRAS, which is a food status, not a cosmetic permission.

→ Clove bud oil in the database: full physical data, 128 suppliers and suggested blends.

What this article does not establish

• GHS classification of mixtures follows its own rules, so the absence of H317 on the oil is not necessarily a labelling gap. The point is that a user cannot read that field alone, not that the catalogue is wrong.
• The three longevity figures come from different suppliers' blotter records, not one controlled experiment. "The oil outlasts eugenol" is a direction, not a quantity.
• The review's "at least 50%" generalises across origins and extraction methods. The actual proportion in your lot is a question for the COA.
• 0.031% is the lowest positive concentration in an already-sensitised population in that study. It is not a safety limit and not a threshold for the general public; IFRA and EU limits rest on other evidence.
• The borrowed boiling point is inferred from the numbers matching. I have no access to the original measurement records.