Teeth whitening. How old should you be? Are there alternatives? My sixteen year old daughter is continually begging me to whiten her teeth. I told her that I don't think she is old enough. Are whitening strips harmful? What would be a good alternative?

Yes. You can successfully whiten your teeth once all of the permanent teeth are completely erupted which is around 15-17. If your daughters teeth are completely erupted she will be fine. You should see your dentist for a professional cleaning and get their opinion.
Typically . Typically we tell our patient's 16 Y.O. I would start with an over the counter whitening system first such as the whitening strips and see how the results are. Sometimes the results are sufficient.
Sixteen . Sixteen is basically the earliest age to start, so that is not a problem. All professional tooth whitening products contain a type of peroxide to eliminate the stains and whiten the teeth. The difference is in the concentration and the application. Otc strips are not very powerful, but can and do work in many instances. A custom fitted bleaching tray from your dentist together with strong gel will apply the material more effectively and will get better results. Maybe a birthday present for your daughter?
Brand . Brand name whitening strips are generally not harmful to use, as long as you follow the directions on the package. If her teeth are darker than normal, then if she were my daughter, i would not prevent her from using whitening strips as long as they were used in moderation. I would make sure that she does not experience too much sensitivity in her teeth nor soreness on her gums during treatment. Also make sure that she is up to date on her regular dental checkups, as she should be in good dental health prior to her using any whitening technique.
I . I usually begin to entertain questions about bleaching around the age of 16 or after a child has completed orthodontic treatment. I would recommend first seeing your general dentist for an examination and cleaning to make sure that bleaching is an appropriate option for your daughter.
There . There is no harm in whitening the teeth of a 16 year old (sorry!). She is old enough to use any of the whitening choices that exist.