The wasabi spice gets its name from the wasabi plant, which is native to Japan. The plant is also called the Japanese horseradish, and it belongs to a cabbage-type plant family, Brassicaceae.
Genuine wasabi is rarely found outside of Japan, so most of what we call the wasabi spice is a mix of horseradish, mustard, and green food coloring.
However, the vital bit that is common to both horseradish and wasabi is a chemical called allyl isothiocyanate. This is what makes the wasabi super-hot so that your receptors go into overdrive when you taste it.
Receptors sit on the cell surface and act as messengers of sorts that help the cell react to various happenings in its environment.
The wasabi chemical is smaller in size when compared to the capsaicin in chillis. So, while capsaicin would cause hotness you feel on your tongue, the smaller wasabi chemical vaporizes and goes up into your nose where there are many wasabi receptors.
This is when your body starts to experience the different reactions common to eating wasabi! A good example is the introduction of allyl isothiocyanate, the wasabi chemical into the body system.
What happens is that the wasabi receptor, "TRPA1," which is related to the receptor for spiciness in chili peppers, the TRPV1, is stimulated by allyl isothiocyanate.
This results in a series of reactions like parts of your body starting to itch, you may begin to cough, choke, or even cry!
If you were wondering, The TRPA1 receptors are not limited to reacting to just wasabi. They typically respond to things that may irritate our senses e.g., onions, tear gas, and smoke.
This is why the TRPA1 receptors remain a subject of great interest for scientists as they hope that understanding the way it works will help in the search for effective pain relief for people with chronic pain.