Spicy heat in food comes in two distinct 'everyday' forms. Chili peppers contain capsaicin, which is a heavy, oil-based molecule that binds to the tongue and throat. This creates a lingering 'burn' that is not easily washed away. Wasabi, horseradish, and mustard, however, contain allyl isothiocyanate. This is a small, volatile molecule that turns into a gas and travels up through the back of the throat into the nasal passages. This is why wasabi creates a 'nose-tingle' or 'brain-freeze' sensation that dissipates very quickly. Interestingly, most 'wasabi' served in restaurants is actually regular horseradish dyed green, as true wasabi (*Eutrema japonicum*) is extremely difficult and expensive to grow.