what keeps my nose from falling asleep?

Not exactly sure what the question is but the answer might be coffee beans!

I'm afraid the coffee beans idea is a complete myth - coffee is a hugely complex smell with more chemical components (about 650) than many perfumes so it's no different from smelling another fragrance.

The way we manage when learning the smell of the big molecule, heavy synthetics like the musky, ambery, types is to dilute heavily (the pure form may not smell at all) and then to smell in short bursts and get a fresh-air break in between.

Your nose will stop smelling any molecule it is exposed to over a long period: even the notorious hydrogen sulphide, which is the bad-eggs smell detectable in tiny amounts and is a tiny molecule, will still not be smelt after a while. It's just that these large molecules at the limit of our ability to detect an aroma tend to do it more quickly.

Hope that helps

Very interesting. And I had always been told to use the coffee beans method to beat olfactory fatigue. However, your advice makes a great deal of sense. Thank you.

I suspect, though could certainly not prove, that the coffee bean idea came about because no perfumery counter or boutique wanted to send customers outside for a breath of fresh air, for fear they would not come back in.

So when someone came up with the clever wheeze of the coffee beans, others followed suit and before you know it an urban myth was born.

People commonly use coffee beans in the refrigerator too. The idea is to annul other smells (mostly bad). I do not know why, but in fact, psychologically or not, it works.

I find many of the synthetic ingredients difficult to smell until I put them in dilution. Don't ask me for the science behind it; I have no idea why it works, but you might give it a try.

In this case, you probably won't smell hydrogen sulfide twice not because of your nose fatigue, but because you would most certainly be dead

The science behind nose fatigue is mostly receptor desensitization. Olfactory receptors are G protein coupled receptors that trigger downstream events in the olfactory neuron by activating and sending off a small G protein. When receptors are activated chronically and en masse, the G protein gets lazy and no longer does its errand. This is called decoupling. Receptors bound to the aromatic molecule it's supposed to recognize can also get removed from the cell surface and sent into "solitary confinement" in a small isolated vesicle inside the cell. This is called internalization. Basically the cell reasons that if you don't seek to avoid that scent, then it's not dangerous, and you don't need to be alerted to its presence anymore.

Not certainly - only if the concentration gets too high. Extremely noxious farts smell the way they do because of H2S - the body can survive high enough levels that you may wish you were dead without actually killing you.

I wonder if its possible to die from overexposure to flatulent emissions.

OP - I don't think that olfactory fatigue depends on whether something is a base note or not. It only depends on how much you are smelling it. I think that if you apply a fragrance such that you are always smelling it (rather than just getting an occasional whiff) then you will get olfactory fatigue.

I think perfumers just take breaks to reset their noses. Chris is real live perfumer - read his comments above.


By the way, Chris - do you do bespoke fragrances that are non-IFRA compliant?

Well, actually in that case a number of organic compounds containing sulfur or the "SH" group are emitted (like thiols or organic sulfides), H2S is present in really low concentration, and probably not the first responsible of the bad smell.
What I was referring to is the fact that if you get your nose's receptors stuck with H2S maybe it means that it's present in enough concentration to kill you (LD50 for hydrogen sulfide is 800ppm)
This doesn't mean you are not able to smell it even in very low concentrations of course, since its odour threshold is 0.47ppb

You obviously know your shit, sir. I defer to your superior knowledge of the subject.

Oh lol, please don't, we're all here just to share our own pieces

Some interesting facts in this article chems
I particularly like the comparison to adaption to the feel of the fabric of your clothes otherwise they would annoy you all the time.

fresh air. you can speed the process up a bit by doing some exercises, preferably outside. edmond roudnitska recommended running up and down a flight of stairs a few times.

but of course, it's best to avoid fatigue from happening. please note that some substances/molecules are more troublesome than others.

naturals are tricky. you will still smell them, except perhaps some molecules. with a single synthetic molecule, you know it when you don't smell it. but in a mixture like every essential oil, it's different. you might get the wrong impression! always be careful, and use your memory when smelling, not just your nose.

Interesting that it is a myth for I had always thought the coffee beans worked.... not as another fragrance but because they are a smell we recognise so well. More like a grounding experience, a re-zeroing of the nose so to speak. Others advocate sniffing your own skin for the same reason I presume. One could almost say that fresh air was a smell too in a way.

You need fresh air + time. Skin + time. + Anything + time…

The coffee has a more instant effect. It has a recognizable smell. But it has also a powerful stimulant drug (caffeine). Studies indicate that the smell of coffee, by itself, can wake a person ...

The olfactory fatigue, say, generally occur from the moment in which the brain does not detect anything dangerous. Maybe the smell of coffee, with its association to caffeine, make the brain go on alert again ...

Or not ...

The matter is to understand if in these cases the receptors are actually oversaturated or if it's the brain which becomes unable to translate the messages into a smell. If the second is true than the coffee trick may work in the way Luìs suggest.
It would be nice to have Luca Turin's point of view on this, since it's very close to what he actually studies; I know he is part of the forum, though I don't think he reads us often

I wondered if it was the contrast of the sharp smell of it compared to the frag. An extreme example of such a thing would probably be victorian smelling salts designed to arouse you from an unconscious state. These were ammonia solids or aromatic ammonia spirits. I wonder how these worked on the body. @Otocione, you would know that I'm sure.

The reason that Coffee Beans work (if they do) is because that have a very different smell to a usual fragrance. I always found that by smelling several very different smells one after another I could extend the time before olfactory fatigue kicked in. Also, like everything else, the more you do something the better you get at doing it. Perfumers do get olfactory fatigue but not as often as those folks who don't smell stuff as much, and Perfumers recover more quickly.

Why it occurs, is another matter. However our smell detectors work I think that sometimes they get clogged, resulting in the inability to smell a specific molecule. SOme molecules clog faster and for longer than others (Methyl Ionone and Iso E Super, are two good examples of molecules quickly causing fatigue). If you have patience your sense of smell will return.

I have a personal experience of the dilution effect. There is a speciality chemical called Karanal (used to be made by Quest, when Quest existed). It was presented at a British Society of Perfumers one day symposium many years ago, and we were told that only 40% of people could smell it. The reaction in the room proved this. I was one of those who couldn't smell it. The concentrated material on a smelling strip was, to me, odourless; whilst others were gagging at the strength of it. I finally smelled Karanal when we were testing its retention on cloth. 0.2% of a 10% solution of Karanal was put into Fabric Softener. A piece of towelling was washed in this Fab Con, and a panel had to smell the wet cloth, the 24 hour dry cloth and the 5 day dry cloth. I could smell nothing out of the jar. The wet cloth was vaguely woody. The dry cloth overpowering. I don't know how much Karanal was left on the dry cloth, but it was enough for me to smell it. Any more was too much.

Good story. I have much the same thing with raspberry ketone - concentrated I don't smell it at all, even down to a 1% dilution I still get nothing. Yet a strip that has had that solution on it for a few days will smell strongly to me of raspberry jam and will continue to do so for weeks.

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What I had in mind here was the experience, which at one time I had frequently, of driving past a steel works on the motorway and being overpowered by the foul smell of H2S - yet if I visited the town next to the factory I would not smell it within a few hours and people who lived there didn't notice it at all unless they went away for a holiday, when it would seem strong for a while after they returned.

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Yes I do. It is to maintain the freedom to do that, that I have refrained from joining IFRA UK - it is a condition of membership that you don't design formulas that are non-compliant, regardless of the client brief. I think that's an unreasonable position, as the point of the Standards is to ensure that consumers are not exposed to anything that might result some small percentage of the population becoming sensitised. One person can, and should be allowed to, take their own judgement on whether a fragrance designed exclusively for them is acceptable to them or not.

Rotorua in New Zealand has a very powerful stench of sulphur akin to rotting eggs, but when you stay there for a while it becomes barely noticable.