Which onions make you cry the most? Onion Facts. Why do we cry when you cut onions? To help you to answer them, Kids video show is answering these questions with 3D animation HD video. When you cut an onion, it releases a gas, when mixed with certain enzymes in the onion, it creates a sulfur gas. These gases then get to your eyes and create a mild acid which irritates the eyes.watch this video at :-https://youtu.be/OhN33LV6vQo