If you have ever watched someone pick cilantro out of their food one leaf at a time, you may have assumed they were being difficult. Many of them aren’t. Their sense of smell is doing something yours isn’t, and the explanation turns out to be fairly ordinary biology.

The aversion is not universal and it isn’t evenly spread. A 2012 study published in Flavour , which surveyed more than 1,600 young adults, found that the share of people who dislike the herb ranged from about 3% to 21% depending on background.

That 21% figure — roughly 1 in 5 — was the ceiling, recorded among participants of East Asian descent, and the survey asked about dislike rather than soapiness specifically. The two track each other closely, but they aren’t the same question.

The lowest rates turned up among people of Middle Eastern, Hispanic and South Asian background. Those are also the cuisines that use cilantro most heavily, which makes the causation hard to untangle. It may be that people who don’t mind the herb cook with it, or that people who grow up eating it learn not to mind.

What’s more interesting is that the soap comparison isn’t an exaggeration. It is close to chemically literal.

What’s Actually In The Cilantro Leaf

Cilantro leaves contain a high concentration of aldehydes, which are small molecules that evaporate easily and do most of the work of smell. A 2005 study published in the Journal of Separation Science , which used a gas chromatograph paired with human sniffers to work out which compounds define coriander’s aroma, found the leaf’s signature comes largely from a subgroup called the (E)-2-alkenals. Across the flavor-chemistry literature, the descriptors those compounds attract in isolation are consistent: fatty, pungent and soapy.

That isn’t a quirk of vocabulary. Related aldehydes genuinely occur in soaps and lotions, partly because the fats those products are made from break down into compounds of this kind over time. The overlap between what an old bar of soap smells like and what cilantro smells like is a real one.

So everyone eating cilantro is taking in the same soap-adjacent chemistry. The question is not why some people notice it. It is why most people don’t.

Why The Same Molecule Lands Differently In Cilantro’s Case

Smell depends on receptors. The human genome carries roughly 400 working olfactory receptor genes, each producing a protein that binds a particular family of airborne molecules. What you experience as a smell is really a pattern of which receptors a molecule happens to activate.

These genes vary more between individuals than almost any other part of the genome. A 2019 study published in the Proceedings of the National Academy of Sciences , which sequenced the full olfactory receptor repertoire in 332 people, found that variation in a single receptor was frequently enough to change how intense or pleasant a given odor seemed.

The practical effect is that one smell can be obvious to one person and nearly undetectable to another. Biologists call the extreme version of this specific anosmia, a blind spot for a single smell in a nose that otherwise works normally.

Cilantro looks like the reverse of a blind spot. A 2012 study published in Flavour , which compared the genomes of more than 14,000 people who had said whether cilantro tasted soapy to them, pointed to a cluster of olfactory receptor genes on chromosome 11.

One of them, OR6A2, binds several of the aldehydes that give cilantro its smell. The leading interpretation is that certain versions of that receptor are unusually sensitive to the soapy notes, so those notes end up dominating everything else in the leaf.

This is where it’s better to be honest than tidy. The genetic signal is real and it has been replicated, but it is small. In that same study, the variant explained roughly 0.5% of the differences between people, and the heritability captured by common variants came in under 10%.

A 2012 study published in Chemical Senses , which looked at 286 pairs of twins, points toward a larger genetic contribution than that, though its own authors note the estimate only holds if you assume shared environment counts for nothing.

There are also preliminary reports linking variants in bitter taste receptor genes to cilantro dislike, though nothing on the footing of the chromosome 11 result. This is probably a trait with several genetic contributors rather than a single switch.

The rest is learning. Whether a smell registers as appetizing or off-putting depends heavily on what your brain has previously filed it alongside, and those associations can shift with repeated exposure in a setting where nothing has gone wrong. People who say they came around on cilantro usually describe something like that. It is a slow accumulation of meals where the herb wasn’t the problem.

There is also a practical note worth passing along. Crushing cilantro, the way you would when making a chutney or a blended sauce, damages the leaf and releases enzymes that convert those aldehydes into other compounds.

A 2010 study published in the Journal of Agricultural and Food Chemistry found strong activity of exactly this kind of enzyme in coriander leaves, with the soapy aldehydes dropping as the corresponding alcohols rose when the leaves were cut and heated. The chemistry is solid. Whether crushing does the same thing fast enough to change what a soap-taster experiences at the table hasn’t really been tested, but it costs very little to try.

The broader point is that flavor isn’t a fixed property of food waiting to be perceived correctly. It is what happens when a particular set of molecules meets a particular set of receptors, and the receptors are not the same in everyone. When someone tells you the salsa tastes like soap, they aren’t misjudging the food. They are accurately reporting what their own nose is telling them, which is not what yours is telling you.