Musk anosmia: why some people cannot smell your base

You build a base, love it, and hand it to a friend who says it smells of nothing much. Neither of you is wrong. This is the one quirk of perception that will actively mislead you at the bench.

Most smell blindness is total — a head cold, an injury, age. Musk anosmia is not that. It is specific: a nose that works perfectly well on everything else has a gap for one particular molecule. Someone can smell bergamot, vetiver, jasmine and vanilla exactly as you do, and be unable to detect a musk you find overwhelming.

It happens with a handful of materials. It happens with musks more than anything else, and often enough that you must design around it.

How common

It depends entirely on the molecule, and the published figures vary a great deal. For some individual musks the reported proportion of people who cannot smell them at all runs into the tens of percent — for a few, studies have put it as high as a third. For others it is a small minority. There is no single number, and anyone quoting you one for "musk" in general is flattening something that differs molecule by molecule.

What is not in doubt is the practical consequence: in any group of ten people smelling your perfume, it is entirely normal for one or more of them to be missing part of your base.

Why it happens

Smelling is done by a large family of receptors, and which versions of them you have is partly inherited. Lose or vary the receptor that responds to a given musk and that musk goes quiet for you. It is genetic, it is ordinary, and it is not a defect — musk anosmics are not missing anything else.

Exposure can shift it. Repeated, deliberate smelling of a musk you cannot detect sometimes brings it partly into range over weeks. Sometimes it does not. Do not count on it.

The trap this sets for a perfumer

Here is the failure, and it is worth reading twice.

You cannot smell your musk. You add more. You still cannot smell it. You add more again. Eventually something reads — perhaps the solvent, perhaps a facet you can detect — and you stop, satisfied. You have just built a perfume with three or four times the intended musk level in it, and everyone who can smell it is now standing in a fog.

The reverse happens too, and is subtler: a perfumer who is unusually sensitive to a musk under-doses it, and the perfume has no floor for anyone else.

The four rules that follow

1. Dose musks to a number, never to satisfaction. Decide the percentage from the formula's structure, weigh it, and leave it. Your own nose is not the instrument here.
2. Blend across families. A base carrying a polycyclic, a macrocyclic and an alicyclic musk is very unlikely to disappear for anybody — the anosmias do not overlap neatly, so where one goes silent another still speaks. This is the real reason professional bases stack several musks rather than reaching for the best one.
3. Get a second nose, every time. Not a compliment — a reading. "Is there anything under this?" is the question. Two or three people costs you nothing and settles it.
4. Find out what you cannot smell, and write it down. Get samples of half a dozen musks from different families, smell them neat on a blotter, and note which ones do nothing for you. That list is a permanent fact about how you work, and it belongs next to your scales.

The strange part

Escentric Molecules built an entire commercial proposition on this. Molecule 01 is essentially Iso E Super alone — another material a significant number of people cannot smell — and the fact that some wearers cannot detect their own perfume while others can became the story rather than the flaw. A perception gap sold as intimacy.

You do not have to be that clever about it. You only have to know it is happening.