Why do cutting onions make our eyes water?

Cutting onions makes our eyes water because tiny particles from the onion get into the air and touch our eyes.

When you cut an onion, you're breaking it apart. Inside the onion are lots of little cells, like a big bag full of small bags. Each cell has a liquid inside that smells strong. When you cut through the onion, you break those cells open, and they release their smelly liquid into the air.

This liquid is not just any liquid, it’s special because it can make our eyes water. It's like when you get sand in your eye, it makes you blink and cry. The particles from the onion are a bit like that sand, but much smaller. They float up to our eyes and cause them to water so we can wash them away.

Our eyes water because they want to clean themselves out. When something tiny and smelly gets in our eye, it feels uncomfortable, and the eye sends a message: “I need more water!” So it starts making tears to help wash away the tiny particles from the onion.

It’s like when you get soap in your eye, you blink and cry too!