capsaicin, which is a waxy substance
that is solid at room temperature. It
dissolves in fats but not water, so it tends
to stay put, coating your tongue and
the roof of your mouth. Wasabi, on the
other hand, contains allyl isothiocyanate,
which is a much lighter molecule with a
freezing point below -100ºC. Although
it is still liquid at body temperature, it’s
much more volatile and some of the allyl
isothiocyanate will always evaporate and
make its way up into your nasal
passages.
