When the cells in these roots are ruptured—if they’re chopped or chewed, for example—they release a compound called allyl isothiocyanate. As well as having a very pungent taste, this chemical is what irritates your nose and eyes, says T. Page Owen, PhD, chair of the Connecticut College Botany Department.
As we eat wasabi or horseradish, allyl isothiocyanate vapors travel through the back of the mouth and up into the nasal cavity. This triggers a nerve response in the nose and sinuses, explains Dr. Dawn Chapman, project leader for sensory research at the National Food Laboratory, causing the familiar nose-tingling burn.