A whitening pen is a tube of whitening gel with a brush tip. The gel comes in different strengths, and some options are peroxide-free to eliminate tooth sensitivity. You paint the gel onto each tooth and wait 60 seconds for it to dry before closing your mouth. After the recommended treatment time, some brands ask you to rinse your mouth or brush your teeth with water — no toothpaste — while other gels dissolve after a specified time. Strips have been around for over 20 years and come in various strengths. You can find peroxide-free formulas like whitening pens if sensitivity is a concern. The whitening agent is pre-applied to the strip, so all you need to do is remove the backing and, starting at the center, press the strip onto your teeth, making sure it touches as much tooth surface as possible. Once your treatment is complete, simply remove the strips and throw them away. Most brands recommend rinsing your mouth with water to remove any remaining whitener. Pens and strips are affordable, easy to use, and widely available online and in most drugstores. After you finish each whitening session, it’s best to wait to eat or drink for at least an hour because your teeth are more susceptible to staining after a whitening treatment.