What causes tears when cutting onions?

Answer 1

Onions contain oils which are irritants to sensitive parts of the body. When you cut an onion, it releases the oils into the air and when it reaches you eyes, it irritates them. The body responds by washing the eyes with tears.

Answer 2

Tearing is caused by the sulfuric compounds contained in the onion, which are released when the onion is cut. Different varieties are more of a problem than others. The higher the level of sulfur content in an onion the more of a problem tearing will be. Dry storage onions have the highest level of sulfur, which makes them cause more of a tearing problem when slicing and chopping. Shown below are some suggestions for solutions to tearing problems.

Chill the onion for at least 30 minutes before cutting. The sulfuric compounds contained in the onion do not react with the air as quickly when they are cold.
Trim off stem end and peel down to the root end. Leave root end on as long as possible because that is where the sulfur is most heavily concentrated. If possible cut, slice or chop the onion as much as possible before removing the root end.

Additional tear saving tips: (Experiment with these tips and see what works best for you!)

Slice under cold running water.
Peel the onion, cut in half and let soak in water for approximately 10 minutes before cutting.
Light one or two candles in the area you are cutting the onion.
Be sure to use a sharp knife to expose less of the sulfur compounds to the air.
Have a fan blowing the fumes away from you.
Place cutting board on the stove top and slice or chop onions with the exhaust fan running.
Use white distilled vinegar to brush down the cutting board before slicing and chopping onions
Try holding your breath while you are cutting the onion.
Keep your mouth closed while you are slicing or chopping onions.
Use a food processor for chopping.
Wear safety or swim goggles. Glasses and contact lenses may also help.

Answer 3

The oil that gives the onion its flavor is actually intended to keep root eating rodents and the like from eating the bulb. When you cut the onion this oil sprays into your eyes, irritating the hell out of them - tears result.

You can reduce or eliminate the spraying oil by putting the onion in the freezer for a little while before cutting.

Answer 4

The active ingredient in onions mixes with your eye fluid and makes sulfuric acid. This is what causes the burning and tears (your body's natural reaction to expel it).

To avoid this, run cold water in the sink, and cut the onions as close to the stream as possible.

Answer 5

As onions are sliced, cells are broken open. Onion cells have two sections, one with enzymes called alliinases, the other with sulfides (amino acid sulfoxides). The enzymes break down the sulfides and generate sulfenic acids. Sulfenic acids are unstable and decompose into a volatile gas called syn-propanethial-S-oxide. The gas then dissipates through the air and eventually reaches one's eye, where it will react with the water to form a mild solution of sulfuric acid. The sulfuric acid irritates the nerve endings in the eyes, making them sting. The tear glands then produce tears in response to this irritation, to dilute and flush out the irritant.

Swim goggles work great as Erica C suggests

Answer 6

onions have high levels of sulfur compounds. It's the pyruvic acid in the sulfur that causes tears, harshness, and indigestion.

Answer 7

Onions put out a gas that makes your eyes watter.

Answer 8

The oils released into the air irritate the eyes.

Answer 9

onions have this defense mechenism where when you cut ino it it makes them do that to protect the onion
i might be wrong though

Answer 10

Old trick fo rpreventing. Keep your mouth closed. Do not open it to talk or breathe and wash your hand sbefore you open your mouth again