What is the whitening ingredient in the pen? How does it work? June 17, 2021 13:32 Updated The enamel safe formula contains 3% hydrogen peroxide, a professionally recommended whitening ingredient. Related articles Do my teeth have to be dry before doing the treatment? Can I use this with a mouth guard or Invisalign type of braces? Do you need to brush your teeth before eating in the morning after using the pen? Am I allowed to eat or drink after application? Is there any minimum hour of sleep I need to have for the product to work? Comments 0 comments Article is closed for comments.