Material guide: lemon oil — three words in the odour field, five in the notes field

CAS 8008-56-8, 74 suppliers, FEMA 2625. Its odour field reads citrus, lemon, lemon peel: three words, where materials with 50 or more suppliers carry a median of eight. That is not a sloppy record. It is a material whose name is already its own descriptor, so no other word is needed to say what it smells like. The notes field is equally short: Do not use on skin, five words about furocoumarin phototoxicity. Its substantivity is 4 hours, among the shortest of the corpus's top fifty materials, and its optical rotation of +57 to +65.5 comes from the 90-plus percent d-limonene. Its shelf life is only 12 months. The corpus uses it in 127 formulas at a median dose of 4.44%.

About a 4 minute read.

The short version

Name: lemon oil, CAS 8008-56-8, 74 suppliers, FEMA 2625, FEMA GRAS
Cold-expressed from the fresh peel of Citrus limon
Odour type citrus; odour: citrus, lemon, lemon peel, three words
Medium strength (rank 2), substantivity 4 hours, optical rotation +57.00 to +65.50
Specific gravity 0.849–0.855, refractive index 1.472–1.474, shelf life only 12 months
The notes field says one thing: Do not use on skin.
127 formulas in the corpus at a median dose of 4.44%

Three words in the odour field

The odor field reads:

citrus; lemon; lemon peel

Three words. odor_descriptions is shorter still: citrus lemon, two.

I counted: 293 materials have 50 or more suppliers and an odour field, and their median word count is 8, with quartiles at 6 and 9. Only 16 (5.5%) run to three words or fewer, and lemon oil is one of them.

The shortest in that group look like this:

Words	Suppliers	Material	Odour field
1	109	vanilla extract	vanilla
1	88	peppermint oil	peppermint
1	53	garlic oil	garlic
2	53	allyl isothiocyanate	pungent; mustard
3	74	lemon oil	citrus; lemon; lemon peel

The pattern is visible: these are the materials whose names are already their own descriptors. Vanilla smells of vanilla, peppermint smells of peppermint, lemon smells of lemon. Describing them needs no other word, because the word already exists in everyday language.

For contrast, ylang grade I carries ten words: floral, petal, jasmin, neroli, lily of the valley, spicy, balsamic, earthy, woody, winey. No everyday word points at it.

What the odour field's length measures is not how complex a material is, but whether a ready-made word exists for it.

One sentence in the notes field

The notes field, with the TSCA definition stripped out, is five words:

Do not use on skin.

No explanation, no concentration limit, no conditions.

The mechanism behind it is furocoumarins, mainly bergapten and oxypeucedanin. These absorb UVA and then form adducts with skin DNA, producing a delayed phototoxic reaction: it appears after sun exposure, blisters, and leaves pigmentation behind when it clears.

Naganuma and colleagues studied lemon oil's phototoxicity specifically in Arch Dermatol Res in 1985 (PMID 4096528). In 2001 Kaddu and colleagues reported a more direct case in J Am Acad Dermatol: someone used bergamot oil in aromatherapy and developed a bullous phototoxic reaction (PMID 11511848). Same mechanism, same plant family.

Practically:

For anything going on skin, buy the furocoumarin reduced record (15 suppliers, CAS 68916-89-2)
Or the terpeneless one, whose notes field reads Furo Coumarin Free.
Rinse-off products (shampoo, soap) carry far less risk, because contact time is short

The 4 hours and the +57 degrees are the same fact

Field	Value
Substantivity	4 hours @100%
Optical rotation	+57.00 to +65.50
Shelf life	12 months

All three point at one constituent: d-limonene.

It makes up more than 90% of expressed lemon oil, which is what the folded oil record's notes field says. Limonene is strongly dextrorotatory, which drives the whole bottle past +57. It is also the most volatile part, which is why substantivity is 4 hours. And it autoxidises in air, which is why the shelf life reads 12 months where most materials read 24.

(Incidentally, +57 to +65.5 is not high for a citrus. Sweet orange peel oil reads +94 to +99, and orange oil terpenes +92 to +105. And sweet orange peel oil folded drops to +78 to +91, the same limonene-removal signature showing up in a different citrus.)

What it appears alongside

Most frequent company across the 127 formulas:

Material	Count	Material	Count
dipg (solvent)	67	benzyl acetate	35
linalool	53	patchouli oil	32
linalyl acetate	42	citronellol	28
coumarin	38	lilial	26
bergaptene-reduced bergamot	37	hedione	25

Coumarin fourth, lavender's linalyl acetate third: this is the cologne and fougère skeleton. Lemon's job in it is the first thirty minutes.

The median dose is 4.44%, quartiles 2.00–8.00%, maximum 50%. The overall median I measured is 2.11%, so it goes in about twice as heavy as an average material. It does not last, so you need more of it to be heard.

What this doesn't establish

"Word count measures whether a ready-made word exists" is my reading, not the database's. I used the word-count distribution across 293 materials as support, but that only shows lemon oil is short, not why.
The phototoxicity mechanism comes from the papers, not this database. The notes field is five words and gives no reason.
I did not look up IFRA's usage limits for lemon oil. Do not use on skin is this database's wording; actual regulatory limits are in the IFRA standards.
"Limonene is more than 90%" comes from the folded oil's record, not this one. I joined two records.
The link between optical rotation and substantivity is an inference. Both correlate with limonene content, but I ran no compositional analysis.
The 127-formula merge excludes lemonile, precyclemone b and isocyclemone e, which are synthetics with lemon-like names rather than lemon oil.