In chemistry, the term for the class of chemicals that includes MACE and tear gas is lachrymator. It is often listed as a hazard for materials that cause tearing and spasms of the eyelids. I got hit with the vapor of phenyl isocyanate once when a safety system failed, and my tears flowed like a river, and my eyes couldn't stay open for more than about a few milliseconds! It was the most unusual experience - I was fine, it was literally just my eyes.