onion in anenclosed room knows that it’s sure to make you cry unless you jump through hoops to prevent the acrid sulfur emanating from the cut onion from reaching your eye, such as putting on fans or submerging them in cold milk or water.
This can be an annoyance, but it can also come in handy if you have debris or other irritant caught in your eye. In this case instead of rubbing your eye and risking worsening your condition:
Cut an onion in half.
Take half the onion