WHY DO ONIONS MAKE US CRY?

             Onions enhance the flavour of 

foods, salads and soups. They also offer

medicinal purposes when cooked, 

because they fight against cholesterol.

The only real problem with onions is

that we often cry when we chop them.

          It is not the strong odour of the onion that makes us 

cry, but the case that the onion releases when we this 

member of the lily family.

          The onion itself contains oil, which contains sulphur, an

irritant to both our noses and to our eyes. Cutting an onion

arouses a gas contained within an onion, propanethial S-

oxide    (CH₃-CH₂-CH=S=O), which then couples with the 

enzymes in the onion to emit a passive sulphur compound. It 

stimulates the eye’s lachrymal glands. When this upwardly 

mobile gas encounters the water produced by the tear ducts 

in our eyelids, it produces sulphuric acid.

          In response to the caustic acid, our eyes automatically

blink, and produce tears which flush out the sulphuric acid.

          Another reflex to rid the eyes of a foreign substance, 

that of rubbing our eyes with our hands, often exacerbates

the situation, because our hands are coated with the caustic, 

sulphuric acid producing oil from cutting the onion, which 

we then rub directly into our eyes.

 The process goes as follows:

•    Lachrymatory-factor synthase is released into the air

      when we cut on onion.

•    The synthase enzyme converts the sulphoxides of the

      onion into sulphenic acid.

•    The unstable sulphenic acid rearranges itself into syn- 

       propanthial-S-oxide.

•    Syn – propanethial-S-oxide gets into the air and comes in 

      contact with our eyes. The lachrymal gland become irritated 

          and produces the tears!

Following are easy, tried and true suggestions for 

minimizing the flow of tears:

•     Remove the root area and peel the onion underneath a

       stream of running water, using a very sharp knife. This 

       will help wash off some of the gases that burn your eyes.

• Put your cutting board near your gas cook stove flame  

       before beginning to chop the onions. The gas stove pulls

       the gases from the onion towards the flame. This burns 

       them up without causing you to tear.

• Place a fan so that it blows the gases away from you 

       before they can get in your eyes. Cut the onion in half and

       lay the cut side down on the cutting board.