Teeth whitening is normally safe when supervised; overuse or high concentrations without guidance can irritate gums

https://martinvddt734.iamarrows.com/in-office-vs-at-home-teeth-whitening-your-guide-to-expert-teeth-whitening-gilbert-and-affordable-teeth-whitening-gilbert-az

Teeth whitening is generally safe when monitored; overuse or high concentrations without guidance can aggravate gums and increase level of sensitivity-- follow instructions closely.