Perfume Noir: Between Seduction, Betrayal, and the Suspects in the Bottle

Quite a few molecules lead a double life, sometimes even carrying multiple secret identities. But to your nose — the seasoned olfactory investigator — nothing remains hidden. Unlike your other senses, it has special clearance to your memories and operates beyond your conscious control, which means — unfortunately — you’re excluded from its investigations. Luckily, there’s a list of known culprits. And once you’ve familiarized yourself with it, no note description will ever mislead you again.

Let’s start by taking a closer look at the case of the fruity summer fragrance:

Particularly popular on hot days, citrus scents stage their annual comeback in summertime. When your own perspiration — and that of others — becomes a nuisance, you reach for the bottle, hoping for refreshment. Yet in rare cases, these fragrances can actually intensify the perception of unwelcome body odors. The culprits are sulfur-containing compounds — so-called thiols — which contribute to the characteristic aroma of citrus fruits and are used in perfumery to create lifelike citrus and fruity notes. Similar thiols are also present in our sweat, which explains the subtle overlap in scent. But that alone doesn’t strip them of their appeal. Properly deployed, a slightly animalic or even risqué quality can be downright magnetic. In the end, it’s the dose that makes the poison: at high concentrations, thiols smell strongly of rotten eggs, which is why they’re added to otherwise odorless natural gas as a safety warning. But artfully blended and used in small amounts, our sulfurous friends reveal only their best side in most fragrances. Even winemakers prize them, since thiols give Sauvignon Blanc its unmistakable aroma.

But let’s return to what you really want to know — behind which fragrance notes these musty thiols may be hiding. At the top of our most-wanted list, both in the fruit bowl and in perfumery, is grapefruit, closely followed by guava and passionfruit. While these three accomplices often play a sweaty little trick on us, a fourth fruit challenges us with a thiol of an entirely different caliber.

By now you’re familiar with the modus operandi of our scent molecules and can guess what a lower concentration means — the smaller, the finer. In small amounts, indole releases a floral, sensual sweetness touched by an animalic nuance, giving it a pheromone-like quality. Equally fascinating is the relationship between indole and serotonin, the mood-lifting neurotransmitter also found in chocolate. Hidden within serotonin’s structure lies an indole ring — which may explain why a walk through a blooming garden can feel so uplifting.

Among flowers, white blossoms contain the highest levels of indole: jasmine, tuberose, orange blossom, and gardenia have become true icons of fragrance, symbols of luxury, desire, and vitality, beloved by perfume enthusiasts for centuries. But be warned: there are those who suffer headaches at the mere whiff of these notes. Which is why floral perfumes are best enjoyed with a measure of caution.

Last but not least, let’s give the escape artist on our list the recognition it deserves — geosmin. The name itself reveals the scent: “geo” for earth, “osme” for smell. This molecule is the showstopper of aromas, making its entrance wherever you go.

Geosmin is produced by a single genus of bacteria, Streptomyces. They live mainly in soil, which is why we most often associate geosmin with the smell of forest floor, earth, and dirt. Animals and humans are extremely sensitive to this molecule, able to detect it in the tiniest amounts. If you’re not a fan of beetroot, mushrooms, or carrots, now you know the culprit. But these microbes also thrive in many bodies of water — and we can all agree that water or fish laced with geosmin is anything but appetizing.

For many of us, the note description awakens a deep longing to capture the atmosphere of rainy days. And although the secret behind this trick has been uncovered, none of the perfumers have yet managed to pull it off successfully. You may have come across niche perfumes in recent years claiming to feature a rain note, but what they promise doesn’t quite match reality.

As mentioned before, our nose is extremely sensitive to this scent Houdini. If the concentration of geosmin in a perfume matched the amounts released during rainfall, it would vanish almost instantly. That’s why so-called rain fragrances usually contain larger doses of the molecule — which, in turn, makes them smell earthy again. So when you wear such a perfume, it’s mostly others who might catch a fleeting whiff of “rain” from a distance. On your own skin, you’ll have to settle for forest floor, at least for now.

We’d be tempted to say with a wink that this works best if you’re gifting the perfume. But don’t lose all hope just yet: perfumery is constantly evolving, with new scent molecules and compositions being discovered all the time. The pursuit of the perfect rain fragrance continues — and in the meantime, you can always enjoy the real thing.

So, you can breathe easy! By now you should be familiar with all the pseudonyms of our culprits — at least the ones we know of. Hopefully, your newly gained knowledge will serve you well in your next scent investigation. But don’t be too quick to judge, and please don’t wrinkle your nose the moment you see these notes written somewhere. After all, most notes never stand alone; in combination with others, they’re far less dangerous than they might first appear. With that, we’ll leave you to your own investigations — who knows where they’ll lead you?