How much does a natural actually vary? Measuring 'you never know where your lot falls'

About an 8 minute read.

The biggest thread on r/DIYfragrance this month, 97 replies, is about whether naturals or synthetics are safer. The poster's irritation came from "non-toxic" home fragrance videos on social media.

Most of the thread is people agreeing with each other. One reply is making a different claim from the rest.

"My day job is in toxicology research: 'natural' products are typically MORE dangerous, because you do not know what their concentration of bioactive component(s) is. The amount you need to get an effect from a weak lot could be a poisonous amount from a strong one... and you never know where your current lot falls on the spectrum!" (Benevolentwanderer)

Two others are describing the same thing from different angles.

"Essential oils contain like a shit ton of different aroma chemicals in wildly unpredictable doses" (TryinaD)

"synthetic ingredients... are generally stable and their effects can be expected and repeated." (Academic-Ad2201)

What those describe is not toxicity but variability. And variability can be measured.

(I handled the toxicity question in a separate article, using patch-test positive rates. This one measures something else.)

How to measure it

The database's occurrence field records how much of a molecule is present in a named natural source, in this format:

geranium leaf oil india @ 0.74%; geranium oil bourbon @ 0.31%; geranium rose-scented oil cuba @ 5.50%

1,800 records carry percentages in that field. I split each one, used the first two words of the source name as a botanical key (geranium oil, lavender oil, thyme oil), kept only combinations with at least three distinct origins under one key, and divided the maximum by the minimum.

That gives 806 combinations.

The result

	Fold-spread
Median	7.1x
75th percentile	24.7x
90th percentile	72.5x
Maximum	1,985x

Threshold	Share exceeding
2x	84.1%
5x	58.9%
10x	41.8%
50x	14.4%
100x	7.4%

In more than four combinations out of ten, the same molecule varies more than tenfold across named origins of one botanical.

That is how wide the spectrum is that the toxicologist said you never know your position on.

Some specific ones

Picking materials with many suppliers, which is to say ones you actually buy:

Molecule	In	Origins	Range	Fold
linalyl acetate	lavender oil	6	0.1% – 34.69%	347x
thymol	thyme oil	9	0.2% – 71.84%	359x
geraniol	thyme oil	6	0.04% – 11.8%	295x
alpha-terpineol	clary sage	4	0.2% – 47.4%	237x
1,8-cineole	marjoram oil	4	0.21% – 42.6%	203x
beta-caryophyllene	basil oil	5	0.17% – 48.7%	287x

The lavender row is worth pausing on. Linalyl acetate is one of lavender's principal components, and it ranges from 0.1% to 34.69% across named origins of lavender oil. Lavender oil has 117 suppliers and is the most common first natural material a beginner buys.

When this becomes a safety question

Everything above is a quality question. The next two rows are something else.

Molecule	In	Range	Fold
eugenol	bay leaf	0.1% – 68.93%	689x
estragole	bay leaf	0.03% – 32.8%	1,093x

Both are individually restricted constituents.

Writing about ylang last time I noted that IFRA restricts natural complex materials on the presumed content of restricted constituents inside them. Read that backwards and it says: a fixed dose of bay leaf oil in your formula delivers a eugenol dose that can vary 689-fold depending on the lot you bought.

And nothing on the bottle tells you.

I expected the assay field to show this, and it does not

Before running this I had a prediction: synthetic single molecules would carry narrow purity specs (like "98.00 to 100.00") and naturals would carry wide ones.

I checked. The prediction was wrong.

	Records	Median width of the assay range
Single molecules (has a CAS, name excludes oil/absolute/extract)	21,929	5.00 points
Naturals (name includes oil/absolute/extract/oleoresin)	1,078	5.00 points

Identical. That field does not separate them.

What does separate them is whether the field is there at all.

	Total records	With an assay field
Single molecules	28,667	22,114 (77%)
Names containing "oil"	2,538	474 (19%)

Four out of five essential oil records carry no purity specification at all.

That is more interesting than what I was looking for. Most synthetic single molecules come with a spec you can check against; most essential oils do not. Not a looser spec. No spec.

Why the spread is this wide

Thompson and colleagues studied thyme (Thymus vulgaris) in J Chem Ecol in 2003, and the result explains that 359-fold figure.

Thyme has six chemotypes with marked spatial segregation in nature. Some populations have a single chemotype in majority, but many have two or three.

Their quantitative findings come in two layers. First, phenolic chemotypes (thymol and carvacrol, at the end of the biosynthetic chain) have a significantly lower proportion of their oil composed of the dominant monoterpene than nonphenolic chemotypes (geraniol, alpha-terpineol, linalool), because the phenolic oils contain high amounts of precursors (gamma-terpinene and para-cymene).

The second layer matters more: at sites where a chemotype is not the majority type, the percentage of its dominant monoterpene decreases significantly.

So the composition of the thyme oil you buy depends not only on which chemotype it is, but on the population mix at the site where it was harvested.

That is a botanical quantity, not a quality-control one.

What the commercial side measures

Thompson measured wild populations. A buyer faces a shelf.

Abouelela and colleagues took four commercial lavender essential oils from the Egyptian market and ran GC-MS with chemometrics in Scientific Reports in 2026:

• 54 volatile metabolites identified across 8 chemical classes
• Esters accounted for 11.4% to 46.1% of total volatile composition (about 4x across four bottles)
• Alcohols 24.7% to 42.6%
• Linalool and linalyl acetate, the quality markers, at 33.61%/24.72% and 46.09%/32.65% in the two best samples
• Some samples showed unusually high non-characteristic fatty acid esters and synthetic glycols, suggesting dilution or adulteration with carrier oils or formulation additives

One market, one name, four bottles, a fourfold spread in ester content, and some of them apparently adulterated.

My 347x is across named origins; their 4x is across four retail bottles. The two are not measuring the same thing. They point the same way.

What this doesn't establish

• This is not a conclusion about toxicity. What I measured is compositional spread. Between "varies a lot" and "dangerous" sit dose, route of exposure and individual variation, and I have handled none of them.
• Equally, this does not show synthetics are safer. Several people in that thread described real adverse reactions to synthetics. Variability data does not conflict with those accounts and cannot be used to dismiss them.
• The 806 depends on my grouping rule. Using the first two words of the source name as a botanical key puts geranium oil bourbon and geranium leaf oil india in different groups (geranium oil and geranium leaf). A different rule gives different numbers.
• This field records literature values, not repeat measurements on one lot. It mixes origins, years, analytical methods and papers. It measures the range visible in the literature, not the range you meet buying three bottles. The latter is certainly narrower.
• Reporting bias runs upward. Unusually high or low samples are more likely to get published.
• "At least three origins" is a threshold I chose. Combinations with one or two origins were excluded, and those tend to be less-reported molecules.
• I did not look at measured lot-to-lot variation on the synthetic side. 77% having an assay field means a spec exists, not that every lot meets it.
• I did not dig into why both median assay widths are 5.00 points. A number that tidy is likely a recording default rather than an actual spec, and I have no way to tell them apart.
• Thompson 2003 studied wild populations in southern France, not commercially cultivated thyme.
• Abouelela 2026 had four samples, from one market. Four samples say nothing about a population.
• I ran no GC/MS. This is database fields plus two papers.