I'd never used any sort of tooth whitening strips, so the process at first was surprisingly slimy. I kind of thought they just stuck on like stickers, but I learned they get gooey when wet. Plus, you have to fold part of each strip over the tops of your teeth, which can take a few tries to keep them centered.
After my first application, I didn't feel any tooth sensitivity — but I did feel nauseous.
I think it was anxiety — the idea of accidentally swallowing the chemicals creeped me out, but after reading the ingredients list (things like coconut oil and lemon peel), I relaxed and never felt nauseous again.
Most whitening strips use peroxide to achieve their aim, which can irritate the tooth nerve and cause pain or sensitivity in some people, according to VeryWell Health.
That could be why Lumineux boasts a "certified non-toxic" label, but that doesn't mean other whitening strips, which the American Dental Association supports, are harmful.