No, You're Not Necessarily "Anosmic" to Iso E Super, That Statistic Doesn't Trace Back to Any Real Study

Open almost any thread about Maison Francis Kurkdjian's Baccarat Rouge 540, Escentric Molecules' Molecule 01, or any fragrance built around the synthetic material Iso E Super, and someone will eventually say some version of the same thing: "20 to 25 percent of people are anosmic to it, they literally can't smell it." It's repeated as settled fact across fragrance forums, blogs, and even some retailer copy.

It's a real, specific-sounding number. It's also, as far as this project could trace, not backed by any actual study.

The one real paper about Iso E Super doesn't mention anosmia at all

The most detailed peer-reviewed chemistry paper actually written about the molecule is Stepanyuk and Kirschning's 2019 review in the Beilstein Journal of Organic Chemistry, "Synthetic Terpenoids in the World of Fragrances: Iso E Super® Is the Showcase." It covers the molecule's accidental discovery and its chemistry in real depth. It never once discusses anosmia, and cites no source for a 20–25% figure, because, as far as this project has been able to determine, no such source exists in it or anywhere else findable.

What the real chemistry actually says

The same paper does report something else, though, a real, measured property that's easy to mistake for anosmia if you don't know the difference. Iso E Super has an unusually high odor threshold: about 500 nanograms per liter of air, far higher than most common fragrance materials. An odor threshold isn't a yes/no anosmia switch; it's the minimum concentration a typical nose needs before a smell registers consciously at all. A high threshold means many people genuinely need more of the material in the air, or a particularly sensitive nose, before they notice it, which in practice can feel exactly like "I can't smell this," even though it isn't the same phenomenon as being unable to smell it under any circumstances.

Real specific anosmia does exist, just not proven here

Genuine specific anosmia, a complete, wired-in inability to smell one particular molecule while smelling everything else normally, is real and well studied. The textbook example is androstenone, a steroid-derived compound with a urinous, musky smell: a documented subset of people simply cannot smell it at any concentration, a trait tied to real variation in the olfactory receptor gene OR7D4, still being actively researched today. That's what actual specific anosmia looks like in the scientific literature, a receptor-level absence, not just "not smelling something as strongly as your friend does."

Where Baccarat Rouge 540 actually fits in

Baccarat Rouge 540's own signature isn't built from Iso E Super at all, but from another "quiet," ambroxan-heavy family of materials with a genuinely similar reputation for disappearing on some people entirely. That part of the story is catching up to real science faster: a 2025 paper in Communications Biology identified a specific human odorant receptor, OR7A17, tuned to ambroxide, the compound at the heart of natural ambergris and its synthetic descendants like Ambroxan and Cetalox. Non-functional versions of that receptor gene turn out to be unusually common in some populations, especially in East Asia; people carrying them can still detect the molecule, but perceive it as noticeably less pleasant rather than not smelling it at all.

So the honest version of this story is less tidy than "1 in 4 people are anosmic to it", but arguably more interesting. Real, receptor-level differences in how people experience specific fragrance molecules are a genuine and active area of science. Just not, so far, for the exact number everyone keeps repeating about Iso E Super.