Eli5: When we eat onion why does aftertaste and breath of it stay longer in our month than other food?

Question

When you eat fresh onion and even when you wash your teeth you can sometimes taste it the day after.

In: 3

Answer 1

The smell of bad breath from onions (and garlic) isn’t really coming from your mouth. Garlic and onions contain volatile compounds like allyl methyl sulfide and cysteine sulfoxide that are absorbed through the stomach and enter the bloodstream and then get slowly excreted through the lungs, skin, or urine.

So it’s actually your blood/lungs that stink.