Teeth whitening is generally safe when monitored; overuse or high concentrations without assistance can aggravate gums

https://blogfreely.net/dernesvhbz/how-to-whiten-your-teeth-before-a-significant-event-or-wedding-event

Teeth whitening is normally safe when monitored; overuse or high concentrations without assistance can aggravate gums and increase sensitivity-- follow directions closely.