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What is the response to cutting onions?

Why Do Onions Make You Cry?

Onions contain compounds called amino acid sulfoxides. When an onion is cut, the cells are damaged and release enzymes that break down the amino acid sulfoxides into sulfenic acids. The unstable sulfenic acids then rearrange into syn-propanethial-S-oxide, which is a volatile gas that wafts up towards your eyes and triggers a neural response.

The syn-propanethial-S-oxide irritates the lachrymal gland in your eyes, which makes you tear up as a protective response. So in essence, onions make you cry as a defense mechanism against the irritating gas they produce when cut open. The sulfur compounds in onions are responsible for the pungent, eye-watering sensation.

Onion Chemistry

Onions belong to the Allium genus of plants, which includes other vegetables like garlic, leeks, and chives. All Allium vegetables contain organosulfur compounds called cysteine sulfoxides. The predominant sulfoxides in onions are isoalliin and methanethiol.

When you slice into an onion, the cysteine sulfoxides are broken down by the onion enzyme alliinase, producing sulfenic acids. The highly reactive sulfenic acids then condense with each other to form syn-propanethial-S-oxide.

Syn-propanethial-S-oxide has a very low pH and wafts up towards your eyes, where it binds to sensory nerve receptors. This triggers your eyes to release tears to wash away the irritant.

Why Are Some Onions More Pungent?

Certain onions are more pungent and likely to make you tear up because they contain higher amounts of sulfur. Factors like onion variety, growing conditions, and storage can affect pungency.

  • Onion variety – Yellow onions are generally more pungent than white onions.
  • Growing conditions – Drought stress increases pungency.
  • Storage – Longer storage increases pungency as sugars convert to sulfur compounds.

So a yellow onion that was drought-stressed and stored for months will be very potent and inclined to make you cry when you cut into it.

Tips to Prevent Crying While Cutting Onions

Here are some tips and tricks to stop onions from making you tear up:

Chill the Onion

Put the onion in the freezer for 15-30 minutes before cutting. The cold temperature helps slow down the chemical reaction that produces the irritating gas.

Use a Super Sharp Knife

A sharp knife slices cleanly through the onion, damaging fewer cells and creating less of the gas. Serrated and dull blades crush the onion, releasing more irritants.

Cut Under Running Water

Cut the onion under a stream of cold water. The water washes away the irritating gas before it reaches your eyes.

Cut Near a Fan or Vent

Position a fan or open a window to blow the gases away from your face as you chop. The increased air circulation disperses the irritants.

Wear Safety Goggles

Onion goggles form a protective seal around your eyes, blocking the gases from reaching the lachrymal glands. They’re inexpensive and very effective at preventing tears.

Use Onion Cutting Devices

Special devices like the onion chopper Proteak completely enclose the onion so gases escape through vents in the side instead of towards you. The Vidalia onion chop wizard seals the onion in a plastic container with strategically placed air holes.

Light a Candle

The flame from a candle near your cutting board is said to neutralize some of the sulfenic acids before they reach your eyes. This is less effective than other methods.

Method How It Works
Chill onion Slows down chemical reaction
Sharp knife Less cell damage
Cut under water Washes away gases
Use a fan Blows gases away
Onion goggles Blocks gases from eyes
Onion gadgets Redirect gases away
Light a candle Neutralizes gases

Wear Contacts Instead of Glasses

Contacts cover your eyes better than glasses, preventing irritation. If you only wear glasses, consider popping in contacts when tackling lots of onions.

Chew Gum While Chopping

Chewing gum while chopping onions supposedly limits the vapors from reaching your tear ducts. The exact mechanism isn’t known, but it may redirect some of the gases into your mouth instead.

Rinse Your Eyes

If onion vapors do make it to your eyes, rinse them immediately with cool water to dilute the irritants.

Home Remedies to Soothe Irritated Eyes

If you’re tearing up from chopping onions, try these home remedies to soothe your irritated peepers:

Splash Cold Water

Splash cold water on your eyes to rinse away onion juices and provide relief. Cold water constricts blood vessels, reducing irritation.

Rosewater and Milk Compresses

Soak a cotton ball in rosewater or chilled milk and apply as a compress over your closed eyelids. Let sit for 15 minutes to soothe irritation. The oils have anti-inflammatory properties.

Cucumber Slices

Place chilled cucumber slices over your eyes for 15-20 minutes. Cucumbers have astringent properties that can relieve irritation and redness.

Aloe Vera Gel

Dab aloe vera gel around your eyes. It contains compounds like polysaccharides that help calm inflammation and provide a cooling sensation.

Tea Bags

Used, cooled-down tea bags from black or green tea applied to the eyes can reduce puffiness and soothe irritation. The tannins help constrict blood vessels.

Remedy Method
Cold water Splash or rinse eyes
Rosewater compress Soak cotton ball and apply to eyes
Milk compress Soak cotton ball and apply to eyes
Cucumber slices Place over closed eyes
Aloe vera gel Dab around eyes
Used tea bags Apply to eyes

Preventative Measures For Next Time

Here are some ways to prepare for minimal tears the next time you need to chop onions:

Buy Less Potent Varieties

Opt for sweet, mild onions like Vidalia or Walla Walla over pungent yellow onions. Their lower sulfur content makes them less likely to irritate.

Store Onions Properly

Don’t leave onions sitting out for long periods. Refrigerate them in a mesh or paper bag, as plastic traps gases. Use within a couple weeks.

Freeze Chopped Onions

Chop a batch of onions all at once, then freeze portions to grab from the freezer as needed. No more last minute onion tears!

Cook Whole Onions First

Roast or boil whole onions before chopping. This cooks away some of the tear-inducing compounds and makes them easier on your eyes.

Use Dehydrated Onions

Dried minced, chopped, or dehydrated onion flakes contain fewer irritating sulfur compounds. Rehydrate before cooking.

Buy Pre-Chopped Onions

The hassle of chopping fresh onions may not be worth it for a small amount. Opt for pre-minced or frozen chopped onions.

Wear Onion Goggles

Keep a pair of onion goggles in your kitchen drawer. Put them on whenever onions are on the cutting board for tear-free chopping every time.

Invest in Onion Chopping Tools

From choppers to tubes to gloves, there are many devices designed to spare your eyes from onion vapors. Try a few to find your favorite.


Chopping onions makes you cry due to the release of sulfur compounds that irritate your eyes. Using a sharp knife, rinsing your eyes, and wearing onion goggles can help minimize tears. For next time, prep onions in advance or use milder varieties. With these tips and remedies, cutting onions can be less of an eye-watering chore.