system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't people smell their own bad breath?

Say, you brush your teeth, floss, gargle mouthwash but some pungent smell still resides that you can't smell. Other people cringe at the first whiff. What is it and why can't people smell it if it's coming out of their own mouth?

EDIT: Great explanations, props to ChiSleepyEyes. If people dont take the "lick your wrist" test, then I'll just have to make some uglier faces so they get the hint.
gpt
Mostly because of your brains ability to drown out the sensory noise going on around you. Like when you put on cologne/perfume, chances are you smell it for all of about 15 minutes maybe, then the only people who notice are those you encounter. If you spent all day with the same person then even they might not notice your bad breath. Your mouth and throat are connected to your nasal passage through the nasopharaynx(tube that lets you spew fluids out of your nose when something funny happens) and therefore your olfactory nerves are constantly being bombarded with those smells and your body just tunes them out. Hope this helps!