system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Does teeth whitening actually remove the yellow or just paint over it and is it unhealthy?
gpt
It actually bleaches out stains. Peroxide is the most common whitening agent used (either hydrogen peroxide or carbamide peroxide) and they work by oxidising stain molecules. This breaks the molecules apart.

However your tooth enamel can also be damaged by the peroxide if used too often, too long, or with too much strength. Especially if you have a cavity and the peroxide gets past the outer enamel into the softer parts of the tooth.

So essentially if used properly it's not unhealthy, but has a lot of potential to weaken your teeth leading to severe damage later if used improperly.