Why do onions cause bad breath?

Onions, as well as other members of the Allium family including garlic, shallots, and chives, contain sulfur compounds called thiosulfinates and sulfides. When onions are cut, chewed, or crushed, these compounds are released and come into contact with enzymes in the saliva. These enzymes convert them into other sulfur compounds, such as sulfuric acid, which can cause bad breath.

The bad breath caused by onions can last for several hours, as the sulfur compounds are slowly released and absorbed by the bloodstream. Some people may also experience a slight burning sensation in their mouths and throats after eating onions, due to the irritation caused by the sulfur compounds.

To help minimize bad breath after eating onions, there are a few things you can do:

- Drink plenty of water to help flush out the sulfur compounds from your mouth and throat.

- Chew on a piece of parsley, mint, or gum to help freshen your breath.

- Use a mouthwash that contains baking soda or hydrogen peroxide to help neutralize the sulfur compounds.

- Avoid eating raw onions on an empty stomach, as this can make the bad breath worse.

- If you are planning on eating onions, be sure to brush and floss your teeth thoroughly afterwards.

If you have persistent bad breath after eating onions, you may want to talk to your dentist or doctor to rule out any other potential causes.