• Question: Why do Onions make people cry?

    Asked by FootballFred03 to Andrew, Jade, Jessica, Kevin, Lynn on 16 Jun 2015. This question was also asked by Zlatan Ibrahimovic, jake the cake, 868curc24, kirbykirbo00.
    • Photo: Jess Wade

      Jess Wade answered on 16 Jun 2015:

      Onions are part of a special family of vegetables which is also home to garlic, chives and leeks. These vegetables absorb sulphur from the soil and form a special chemical called a ‘sulfoxide’. When we cut an onion up, it releases a special enzyme (a chemical that speeds up a reaction) that triggers something in the sulfoxides and turns them into acids. Acids are super unstable and break apart. When the little bits of these acids enter the air near our faces it makes us cry! It is so annoying when I’m in my kitchen! You can get special cooking goggles to protect your eyes (my mum got them for me for christmas).

    • Photo: Kevin Honeychurch

      Kevin Honeychurch answered on 16 Jun 2015:

      Onions contain amino acid sulfoxides that form sulfenic acids in the onion cells. Both the enzymes and the sulfenic acids are kept separately in the cells. When you cut the onion, the otherwise separate enzymes start mixing and produce propanethiol S-oxide, which is a volatile sulphur compound that starts wafting towards your eyes. The gas that is emitted reacts with the water of your eyes and forms sulphuric acid. The sulphuric acid thus produced causes burning sensation in your eyes and this in turn leads to the tear glands secreting tears. Thus you end up with watery eyes every time you cut onions at home.
      I found that if you put the onions in the fridge for about an hour before cutting them this doesn’t happen, so no tears………..