What is it in onions that makes you cry?

-- Anna Beecroft, 8, Gaithersburg

Think of your kitchen counter as a chemistry lab, and the onion as a batch of chemicals ready to be mixed.

When you cut an onion, molecules called amino acid sulfoxides and enzymes called alliinases get released from their individual cells within the onion. When they mix together, they form sulfenic acids, which quickly change into a chemical called syn-propanethial-S-oxide. Some of that chemical turns into sulfuric acid, an especially irritating gas.

The waterworks start after the syn-propanethial-S-oxide wafts up toward the surface of your eyes. To fight off things that irritate your eyes, your body has a built-in defense: tears. When the chemical hits your eyes, your tear ducts secrete extra tears to dilute the nasty stuff and wash it away.

Of course, everybody's first reaction when their eyes hurt is to rub them. This isn't such a great idea. If you've been slicing an onion, your hands are probably coated with the offending chemicals, too. Touching your eyes will just make things worse.

Scientists in Japan say they are getting closer to creating a "tearless" onion. They still have a ways to go.

There are all kinds of suggestions for how to keep from weeping when you're cutting onions: everything from wearing goggles (not very practical) to holding a sugar cube or slice of bread in your mouth to absorb the gas before it hits your eyes. You're welcome to try these, of course, but you'll probably just look -- and feel -- silly.

Some say your best bet is to run tap water over the onion as you peel, slice and dice. The running water dissolves the chemicals and washes them down the drain.

But using a knife is tricky enough on a dry cutting board, and things can get pretty slippery under water. So maybe this is a job best left to a grown-up. You could help by standing close by -- with a box of tissues.

-- Jennifer Huget

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