Why does wasabi burn the nose?

Today is February 6th, and it appears that it’s National Chopsticks Day. Yes, it exists. Congratulations to all.

I personally prefer using a fork and knife, and only use chopsticks at sushi restaurants. And when I think of sushi, the first thing that comes to my mind is wasabi sauce, probably because I still remember my first (very hot) experience with it.

So, why is wasabi so harsh on us?
In fact, wasabi’s spiciness comes from the allyl isothiocyanate it contains. This allyl isothiocyanate elicits painful sensations by activating the TRPA1 ion channel (a so-called “wasabi receptor”) in the terminal endings of specialized sensory neurons. This is very similar to how chili pepper’s active ingredient, capsaicin, elicits pain via the TRPV1 ion channel (a pain receptor).

The interesting thing is that, even though both wasabi and chili pepper induce burning sensations, these sensations are different. When we eat it, wasabi primarily burns the nose and upper throat (but also the mouth and tongue), while chili pepper mostly burns the tongue and mouth (and usually doesn’t sting the nose). The reason for this is that, unlike capsaicin, allyl isothiocyanate is highly volatile, and so its spicy vapors travel through the back of the mouth and into the nasal cavity, where they activate TRPA1 and cause pain.

So, what should you do if you accidentally used too much wasabi or chili pepper? The first reaction may be to wash it away with water. And it could be very effective for getting rid of wasabi’s painful sensation, because allyl isothiocyanate is water soluble. In contrast, capsaicin is hydrophobic and fat soluble, so you won’t wash it away with water. A better option is to use milk, cream, or yogurt. Fatty milk will pull capsaicin off the TRPV1 channel and wash it away… It’s in theory. Has anyone tried it in practice? I hope it works.

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