The Scientific Reason Everyone Smells Things Differently

“What’s that smell in this room? Didn’t you notice it, Brick? Didn’t you notice a powerful and obnoxious odor of mendacity in this room?” —Big Daddy, Cat on a Hot Tin Roof (1958)

In A Nutshell

How many times have you had an argument over whether or not a scent is divine or disgusting? There’s a scientific reason for it, and it all has to do with your DNA. Every person’s olfactory system is coded with a specific set of genes, and everyone’s includes different amino acids. These each react to different smells in different ways, meaning that we all are actually smelling the same scents in different ways.

The Whole Bushel

It’s one of those things that you realize without necessarily thinking about. Some people like certain smells, while others find them revolting. There are some people that even love the smell of skunk spray, although most of the population thinks it’s disgusting. It’s meant to be gross, after all, it’s a defense mechanism . . . so why are there people that like it?

It’s not a personal choice, and it’s not (necessarily) just people trying to be edgy. There’s actually a scientific reason for why every person in the world likes different sorts of smells, and that’s because we’re actually, physically smelling them differently.

Researchers at Duke University have tracked down the reason that we all have a different sense of smell, and it turns out that it’s much more complicated than either liking or not liking something—we’re actually smelling things in a completely different way.

They found that there are around 400 genes that are directly responsible for supplying the code for the receptors in our nose. That might not sound like much, but break them down into their smallest increments and there are more than 900,000 different combinations of these smell genes.

The presence or absence of a single amino acid can mean the difference between something smelling good and something smelling bad. To determine just how much of a difference these amino acids make, researchers isolated 500 receptors from 20 different people. They were all slightly different, and in some cases, the only difference was a single amino acid.

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The receptors were then exposed to tiny amounts of certain smells, allowing them to track which receptor reacted to which smell, and showing that how we each receive smell information is very different.

It’s the same outside of the laboratory. When we smell something, the scent enters our nose and hits receptors there. Those receptors relay information to the brain, telling us, among other things, if it’s good or bad.

But with 900,000 different possibilities for how those receptors are programmed, that means there are a lot of different ways we experience lots of different smells.

There’s so much of a variation between people that if you take any two people and compare how they’re set up to smell different things, you’ll find about a 30 percent difference between them. That means that while one might love the smell of fresh-cut grass, it might make the other one physically ill.

The whole process has been likened to our visual system, but on a much more precise scale. Differences in our visual receptors change how we see color—that’s why some people are colorblind. The same principle applies to our sense of smell.

So now that we know why some people love a certain smell and why some hate it, what’s next?

Once scientists can determine exactly what receptors are linked to what scents and what pleasure or disgust responses, they’re one step closer to digitizing smells. A smell can be created not to smell like one thing or another, but to register with certain receptors in the nose, for something that everyone likes or everyone hates.

Show Me The Proof

Medical Xpress: Extensive variability in olfactory receptors influences human odor perception
Medical Xpress: No two people smell the same
Smithsonian: We All Experience Smells Differently From One Another

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