Why do you get tears in your eyes when cut onions?

The chemical composition of onions contains a substance called syn-propanethial-S-oxide (SPSO). When an onion is cut, this chemical gets released and mixes with the water in your eyes, forming sulfuric acid. This acid is what causes the burning sensation and tears in your eyes.

The chemical reaction that takes place when onions are cut is as follows:

* The enzyme alliinase is released when the onion is cut.

* Alliinase converts the amino acid sulfoxide alliin into the gas syn-propanethial-S-oxide (SPSO).

* SPSO dissolves in the moisture on the surface of the eye and forms sulfuric acid.

* Sulfuric acid irritates the conjunctiva, the clear membrane that covers the white part of the eye.

Here are a few tips to help you reduce the chances of getting tears in your eyes when cutting onions:

* Use a sharp knife. A sharp knife will help you to make quick, clean cuts, which will release less of the chemical that causes tears.

* Cut the onion under running water. The water will help to wash away the SPSO before it reaches your eyes.

* Wear goggles or sunglasses. This will help to protect your eyes from the fumes released by the onion.

* Chill the onion before cutting it. This will help to slow down the release of SPSO.