I use one every other night. I don’t think it’s harmful or anything.

Depending on whitch kind you use it can make your teeth sensitive. Same with whitening toothpaste.

It can cause teeth sensitivity and recent research has shown it may cause gum/mouth cancer.

I would use it sparingly if possible.

You can wear down the enamel on the Teeth and they Become OVER sensitive and eventually it will hurt to even breathe air over them, or talk.. follow the directions cookie,

Yes, it is bad.

I have no idea.

I was going to get my teeth whitened BUT, I said heck with that, I’ll get a tan instead!

That is using them a little too much. Aside from the things everyone said, sensitivity and stuff, they also will become ineffective. Your teeth will become so used to them that they won’t work. They really are only supposed to be used like every six months. So lay off them for a little bit and then in a few months use. But give your teeth time to breathe.

I don’t think there is anything wrong with it