The genetics firm 23andMe decided to take a closer look. They analyzed the genomes of almost 30,000 people asking each subject whether they like cilantro and what they thought it tasted like. Subjects who said that cilantro made salsa taste like bubble bath had similarities in a cluster of smell receptor genes that – surprise – detect the smell of soap. They tended to share one gene in particular which codes for the receptor that picks up the scent of aldehyde chemicals. Aldehyde chemicals are organic molecules that contain an aldehyde group, a carbon bonded to a hydrogen and double bonded oxygen. There’s a bunch of different aldehydes that have really distinctive smell. There’s vanillin which smells like vanilla and cinnamaldehyde which is what gives cinnamon its smell. There is more than one aldehyde responsible for giving cilantro its distinctive smell and they also happen to be a byproduct of soap making.