Material guide: oakmoss absolute — the chypre foundation, and the atranol story

First, the name: oakmoss is not a moss. It is a lichen that grows on oaks, another entry in the names-versus-things lesson. Perfumery lore condenses the chypre family into a triangle of bergamot, labdanum and oakmoss; bergamot handles the opening, oakmoss the foundation. This guide covers the foundation itself, and the regulatory story it got caught in.

What matters

• Oakmoss absolute is a dark, semi-solid base note: green, woody, earthy, with shadows of seaweed, hay and tobacco. Longevity on record is 400 hours (measured at 20% dilution), and it is the foundation material of the chypre and fougère families.
• It is also a famous name in fragrance regulatory history: research in 2003 identified the hidden allergen chloroatranol, and in 2017 the EU added the two molecules atranol and chloroatranol to the cosmetics prohibited list. Oakmoss extracts with those two molecules removed remain legal to use today.
• The catalog reflects that history: 42 suppliers carry the real thing, 21 carry replacers, and product names are full of low atranol and IFRA wording. Which one to buy depends on your use and your market.

The basics

CAS	977059-15-6
Source	Absolute of Evernia prunastri (a lichen), natural
Odor	green, woody, earthy, musty, mossy, oily, herbal, seaweed, hay, tobacco
Odor type	mossy
Strength	medium
Longevity	400 hours (at 20% dilution, on a blotter)
Appearance	dark green-brown semi-solid
Flash point	> 93.33 °C
Shelf life	36 months or longer (cool, dark, sealed)
Listings	GRAS, JECFA, FEMA GRAS, IFRA

A natural extract has no single molecular formula, so that blank is normal. Here, 400 hours is the ceiling of the source's scale (the vanillin guide covered this), and this reading was taken at 20% dilution. Semi-solid plus dark-colored means two practical warnings: dilute before use, and expect it to tint pale formulas.

A regulatory story

Oakmoss has been in perfumery for over a century, and allergy cases accumulated for a long time too. The turning point came in 2003, when Johansen and colleagues published a dose-response study in Contact Dermatitis:

Oak moss absolute is reported as the cause of allergic reactions in a significant number of those with perfume allergy. ⋯ Recently, chloroatranol, a hitherto unknown fragrance allergen, was identified in oak moss absolute. 13 patients previously showing a positive patch test to oak moss absolute and chloroatranol ⋯ All test subjects (13/13) developed an allergic reaction at the site of application of the solution containing chloroatranol. Among them, 12/13 (92%) gave a positive reaction to the 5 p.p.m. solution. The dose eliciting a reaction in 50% of the test subjects at patch testing was 0.2 p.p.m. ⋯ Judged from the elicitation profile, chloroatranol is the most potent allergen present in consumer products today.

"Most potent allergen" is the abstract's own conclusion; we quote it as written. Industry first tried to save itself by stripping atranol and chloroatranol out of the extract. In 2009, Nardelli and colleagues tested the limits of that route:

A sample of oak moss was treated by a polymer-based method to reduce the content of the two main allergens, namely atranol and chloroatranol, from 3.4% to less than 75 p.p.m. and from 1.8% to less than 25 p.p.m., respectively. Fourteen subjects with positive reactions to commercial oak moss patch test materials were tested with this sample, diluted 1% in petrolatum: it reacted negatively in six but gave still positive reactions in eight subjects, with the same intensity as the commercially available materials. Conclusions: polymer-based treatment reduces the allergenic elicitation potential in previously sensitized individuals only to a minor extent; the residual concentrations are unsafe for the consumer.

Note the study population: all fourteen were already sensitized. The finding is that a good share of already-sensitized people still reacted to the low-atranol version, not that everyone becomes allergic. Regulation eventually caught up: Commission Regulation (EU) 2017/1410 (adopted 2 August 2017) added atranol and chloroatranol (together with another fragrance, HICC) to the prohibited list of the cosmetics regulation 1223/2009. Cosmetic products containing them could not be placed on the EU market from 23 August 2019, and could not be made available on the market from 23 August 2021.

The key detail: the ban covers two molecules, not oakmoss. Oakmoss extracts with atranol and chloroatranol removed remain usable, which is where the low atranol and IFRA wording in today's product names comes from. Our reading: this was an industrial rebuild that saved the material by sacrificing two constituents, a cousin of ambroxan's whale-retirement story, except the driver here was skin safety rather than conservation.

The family on the catalog

Entry	What it is
oakmoss absolute (42 suppliers)	The real thing: lichen absolute, product names often marked low atranol or IFRA-compliant
oakmoss absolute replacer (21 suppliers)	Blended substitutes that avoid atranol and chloroatranol
oakmoss resin (12 suppliers)	Resin form, thicker
oakmoss concrete (8 suppliers)	The concrete: one stop before the absolute in solvent extraction
oakmoss phenol (7 suppliers)	One of the synthetic mossy single molecules

21 replacers against 42 of the real thing is a market vote, like the ambergris tincture row, except here the original is still ahead.

When you smell it

• To our noses, dilution brings out green and earth first, then hay and a saline, tide-pool edge, and finally a dry, tobacco-like tail. On its own it is not a charmer; in a formula it becomes the ground the whole perfume stands on.
• The semi-solid is awkward to handle. Our approach is a warm water bath to soften it, then a dilution at 10% or below.
• To understand chypre, smell it layered with bergamot: one flies up, one digs down, and in our trials the skeleton appears at once.

Regulatory

Listed in GRAS, JECFA, FEMA GRAS, and IFRA. For skin-bound formulas, read the story above as current law: cosmetics on the EU market must not contain atranol or chloroatranol, oakmoss extracts themselves are governed by the current IFRA Standards, so buy a compliant version and ask your supplier for the specification and allergen data. Non-skin uses (room scents, candles) sit under different limits; national rules still apply.

Buying notes

1. For skin use, pick a version marked low atranol or IFRA-compliant, but the name is not the proof: ask the supplier for the specification and allergen analysis, and confirm it meets your target market's rules.
2. Dilute the semi-solid first (10% or below), and expect tinting; test pale-colored products on a small batch.
3. To practice the chypre skeleton, pair it with bergamot and an amber-labdanum base; to avoid atranol and chloroatranol, the replacer row's 21 suppliers are yours to pick from; their own formulas and rules still need checking.

→ Oakmoss absolute in the database: full physical data, supplier list, suggested pairings. → oakmoss absolute replacer | oakmoss resin | Search by scent: try "moss green woody" to find its neighbors.

References

J. D. Johansen, K. E. Andersen, C. Svedman, M. Bruze, G. Bernard, E. Giménez-Arnau, S. C. Rastogi, J.-P. Lepoittevin & T. Menné, Chloroatranol, an extremely potent allergen hidden in perfumes: a dose-response elicitation study, Contact Dermatitis, 49(4), 180–184 (2003). PMID 14996064

A. Nardelli, E. Giménez-Arnau, G. Bernard, J.-P. Lepoittevin & A. Goossens, Is a low content in atranol/chloroatranol safe in oak moss-sensitized individuals?, Contact Dermatitis, 60(2), 91–95 (2009). PMID 19207379

Commission Regulation (EU) 2017/1410 of 2 August 2017, amending Annexes II and III to Regulation (EC) No 1223/2009 on cosmetic products. CELEX 32017R1410