Wasabi's spiciness comes from a chemical compound called allyl isothiocyanate (AITC) , which is also found in mustard and horseradish, plants from the same Brassicaceae family as wasabi
. When the wasabi root is grated, enzymes mix with glucosinolates in the plant cells to produce allyl isothiocyanate, which is volatile and stimulates the nasal passages more than the tongue, causing a sharp, pungent heat that hits the nose rather than the mouth
. This differs from chili pepper spiciness, which is caused by capsaicin and affects the tongue directly. The wasabi heat is short-lived, quickly fading after a brief nasal sting, which is why the spicy sensation lasts only about 30 seconds and can cause a burning feeling and watery eyes
. The compound's volatility and water solubility mean drinking water can wash away the sensation, unlike capsaicin from chilies
. In summary, wasabi is spicy because of allyl isothiocyanate, a chemical released when the root is grated that stimulates nasal receptors, producing a quick, sharp heat distinct from chili pepper spiciness
