Why does chopping onions tend to end in tears?
It’s a pain we’ve all experienced but few understand – that’s where Twitter expert James Wong comes in handy though.
The self-proclaimed botany geek has posted a thread about why the bulb causes people to cry, and it turns out it all stems from the plant’s chemical defences.
WHY ONIONS MAKE YOU CRY
When you cut into an onion the ruptured cells deploy an airborne, sulphur-based chemical into the room.
When it mixes with the water in your eyes & nose it turns into sulphuric acid.
A chemical defence created by plants.
But there’s even more to it.. pic.twitter.com/BBh5DtuTsO
— James Wong (@Botanygeek) September 18, 2018
So the slicing causes plant cells to rupture, releasing a sulphur-based chemical that reacts with your eyes and nose by turning into sulphuric acid – and the chemical is multi-functional too.
This chemical not only repels mammals who might be attempting to munch on the bulbs, but is also toxic to bacteria and fungi, helping prevent infection at the site of the wound.
As humans we can hijack this chemical & use it to treat microbial infections on our bodies too! pic.twitter.com/yuNAWRnkYA
— James Wong (@Botanygeek) September 18, 2018
So the chemical is also anti-bacterial – worth remembering if you get a cut out in the onion fields.
But it turns out the plant has to be careful with the chemical too.
This compound is so potent however it is even toxic to the plant itself.
So intact onions don’t contain any at all. It is only created at the site of cellular damage when 2 separate chemicals come into contact with each other. Like a 90s glow stick. pic.twitter.com/PyhDTLPm1P
— James Wong (@Botanygeek) September 18, 2018
So until the onions are cut the chemical, which is toxic to the plant itself and causes your eyes to stream, isn’t even there – with great power, comes great responsibility.
Before you go complaining about cutting onions too much though, spare a thought for your elders.
The weirdest thing?
Onions get the sulphur to make these compounds from the soil they grow in.
An important part of the sulphur in U.K. soils came from the sulphuric acid in acid rain. No, really.
So our onions are getting less pungent (& maybe less nutritious) over the years. pic.twitter.com/9qFq4jb9mc
— James Wong (@Botanygeek) September 18, 2018
The rain might be cleaner, but the onions ain’t what they used to be.