Why you get tear when cut onion?

Onions contain a chemical compound called syn-propanethial-S-oxide (SPSO). When you cut an onion, this compound is released and comes into contact with your eyes. SPSO reacts with the water in your tears to produce sulfuric acid, which is what causes the burning sensation and tears.

Here's a more detailed explanation of the process:

1. When you cut an onion, the cells in the onion are damaged and release SPSO.

2. SPSO is a volatile compound, which means that it easily evaporates and travels through the air.

3. When SPSO reaches your eyes, it comes into contact with the water in your tears.

4. SPSO reacts with the water to produce sulfuric acid.

5. Sulfuric acid is a strong acid that can irritate your eyes, causing a burning sensation and tears.

In addition to SPSO, onions also contain other compounds that can contribute to the burning sensation in your eyes. These compounds include:

* Lachrymatory factor (LF): LF is a protein that is also found in other plants, such as peppers and garlic. LF can cause the same burning sensation and tears as SPSO.

* Enzymes: Onions also contain enzymes that can irritate your eyes. These enzymes can break down the proteins in your tears, which can lead to a burning sensation.

The amount of SPSO and LF in onions can vary depending on the type of onion and how it is stored. For example, red onions tend to contain more SPSO and LF than yellow onions. Onions that are stored at room temperature also tend to have higher levels of SPSO and LF than onions that are stored in the refrigerator.

If you are sensitive to onions, there are a few things you can do to reduce the chances of getting tears when you cut them. These tips include:

* Chill the onions before cutting them. This will help to slow down the release of SPSO and LF.

* Cut the onions under running water. This will help to wash away the SPSO and LF before it can reach your eyes.

* Wear goggles or safety glasses when cutting onions. This will help to protect your eyes from the SPSO and LF.

* Use a sharp knife to cut the onions. This will help to reduce the amount of damage to the onion cells and release less SPSO and LF.

If you do get tears when cutting onions, there are a few things you can do to relieve the discomfort. These tips include:

* Rinse your eyes with cold water. This will help to wash away the SPSO and LF.

* Apply a cold compress to your eyes. This will help to reduce the swelling and pain.

* Take an over-the-counter pain reliever. This can help to relieve the pain and inflammation.

If you experience severe eye pain or swelling, you should see a doctor.