• Question: Why does onion make you cry?

    Asked by wizzyg12 to Sam, Matt on 25 Jun 2013.
    • Photo: Sam Geen

      Sam Geen answered on 25 Jun 2013:

      The onion has a chemical in it that irritates your eyes. When you cut one, you spray the chemical into the air, where it mixes with the moisture on your eyes and makes them sting. It can help to run the trap or have some water nearby, as this can help absorb this chemical.

    • Photo: Matthew Pankhurst

      Matthew Pankhurst answered on 26 Jun 2013:

      Yep – that chemical is sulfur dioxide, or SO2, and when it reacts with the water that is on your eyes (why you blink is to keep this water topped up!) it turns into weak H2So4 – which is sulphuric acid – ouch! Cutting onions underwater solves this problem – but it makes a new problem…. it makes your onions soggy….

Comments