Why Does Cilantro Taste Like Soap to Some People?

Cilantro – the leaves and stems of the coriander plant – is one of the most polarizing foods out there. Cilantro lovers – like me – get some version of fresh, herb-y, citrus-y deliciousness, while cilantro haters often refer to it as “soapy”. But why do people have such completely different experiences with this herb? Why soap, specifically?
The common thread here is a group of chemical compounds called aldehydes. Aldehydes tend to be volatile: they’re likely to fly into the air, where they can enter your olfactory system and get sensed. So lots of aldehydes produce strong smells – think formaldehyde or citronellal – and, because smell is a big part of taste - strong flavors; think cinnamon or vanilla. Or, cilantro, because cilantro is packed with a bunch of different aldehydes.
And, coincidentally, some of these particular aldehydes also happen to be the byproducts of a particular step in the soap-making process. So cilantro-haters ARE right: cilantro tastes like soap. But only to some people.

[Direblade]

I was told by people who do like cilantro that it tastes like parsley, like almost exactly.

[Honeneko.]

I love the stuff. I can also taste why some people taste soap. You don't eat it alone, silly Billies and Millies. My father hates the taste of the stronger stuff. Epazote is an herb that's also known as wormseed, Mexican tea, Jesuit's tea, or goosefoot.

[tozzasque]

In italian it's 'prezzemolo', and we use it all the time. So much so that we have a saying: "stai in mezzo come il prezzemolo", "you are doing business like cilantro".