Why do onions make you cry? 3 tricks that actually work

This sets off a chain of reactions that produces a volatile compound called propanethial-S-oxide, also known as the onion’s lachrymatory factor. It travels through the air and reaches the surface of your eyes, where it irritates the nerves. Your eyes respond by producing tears to wash the irritant away. So, what can you actually do about it? Some old kitchen tricks are more folklore than science, but these three have a reasonable basis.