Why does cilantro taste like soap to some people?

One plate of cilantro, two different worlds

Someone sprinkles cilantro on a salad. You pick up a leaf and taste something fresh and green. The person next to you frowns and says it tastes like soap. Same leaf, two completely different experiences.

Where the smell comes from

Cilantro leaves get their smell mostly from a group of molecules called aldehydes: decanal, (E)-2-decenal and (E)-2-dodecenal. Aldehydes are a large family of molecules, and many of them smell sharp and green. Soap and detergent contain the same kind of molecules. So do the smelly sprays of stink bugs. So if cilantro smells like soap to you, your nose is not being silly. It is being accurate.

The difference is in your genes

Inside your nose there are tiny smell receivers called olfactory receptors. They turn molecules floating in the air into signals your brain can read. One of them, called OR6A2, is especially good at noticing those aldehydes. The instructions for building OR6A2 are written in a gene on chromosome 11. If your version of that gene is slightly different, this receptor becomes too sensitive. The same aldehydes that smell like plain grass to other people smell like strong soap to you.

In 2012, scientists studied almost 30,000 people and found gene variants linked to disliking cilantro. About 80% of identical twins agreed on whether they liked it, but only about half of fraternal twins did. Different groups disagree too: about 21% of people of East Asian ancestry dislike cilantro, about 17% of Europeans, but only about 7% of South Asians, who often grow up eating it. Genes set the starting point; the food you eat as a child moves the finish line.

Try it yourself

Ask a grown-up to help you collect three things: a few cilantro leaves, a bar of unscented soap, and a small handful of coriander seeds (the seeds of the very same plant).

1. Smell the cilantro leaves, then smell the soap. Write down your first reaction.
2. Crush the coriander seeds on a piece of paper and smell them. They smell like lemon, because the seeds are mostly linalool, a completely different molecule.
3. Ask everyone at home: who thinks cilantro tastes like soap? Write down the answers and work out the percentage.

It is completely normal for one family to disagree.