The tear gas ethyl bromoacetate is a fruity-smelling alkylating agent that blocks the ability of the frog nose to respond to esters and a variety of other odorants, but leaves sensitivity to amines unimpaired. Lachrymators and chemical warfare agents of other functional types such as sulfides (mustard gas) and amines (nitrogen mustards) may have similarly specific actions that will enable their use as chemical probes of the sense of smell.