Why do onions make us cry?

Cutting an onion can make even a strong man cry. The onion is defending itself.

Inside an onion’s cells are two things kept apart: a special chemical and an enzyme. When you cut the onion, the cells break and the two mix. Together they make a gas that floats up into the air.

When the gas reaches your eyes, it mixes with the water on the surface and turns into a very weak acid. Your eyes feel the sting and do the only thing they can — make tears to wash it away.

To cry less: chill the onion in the fridge first (cold slows the gas), cut under running water, or use a very sharp knife so fewer cells are crushed.