1. 切洋葱前先冷藏或冷冻

According to the Institute, putting onions in the fridge 30 minutes or in the freezer for 10-15 minutes before chopping can prevent the stinging as the cold stops tear-jerking gas from being produced. 

2. 将洋葱浸泡在水中

Another way to reduce the gas released by the onion is to soak in water - although this could compromise the taste. 

3. 最后切洋葱根部

When an onion grows it mixes with sulfur in the soil to create amino acid sulfoxides. These sulfoxides turns into sulfenic acid when the onion is sliced which reacts with the enzymes to create a gas called syn-propanethial-S-oxide. 

As it reaches your face, this irritating gas stings and burns, triggering the eyes to produce tears to flush out the gasses. 

The root is where the fumes are most concentrated so it is recommended that this part of the onion is left on as you chop it to avoid stinging eyes. 

4. 在通风处切洋葱

Another way to reduce the gas’s effect on your eyes is to chop it next to a window or near a fan so the gas is diluted or blown away from your face. 

5. 使用锋利的刀具

And take care to use a sharp knife, this will make it easier to glide through the vegetable, causing fewer cells to be broken and less gas to be released as a result.