system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Many brands for toothpaste and mouthwash claim to be "whitening" what are these doing (if anything) to make my teeth whiter?
gpt
yes they are, but the means by which they do is really, really bad for your teeth in the long run.

some of them use acids, hydrogen peroxide that weakens your top layer of enamel that has been stained and you brush that away like a scouring pad would take wax off of a car. This leaves your teeth very sensitive, and prone to cavities and even chipping. Some of them use harsh abrasives- pretty much like sand paper grit- to etch away that enamel. The only real way to change the colour of your teeth outside of the *proper* way a dentist would, would be to grind it away, and that's what these toothpastes do to your goddamn teeth. Some even have chemicals to counteract the sensitivity/numb the nerves inside your tooth so you don't feel how much of your enamel's been eroded away.

...but at least your teeth are whiter! right?