Whitening strips generally do not damage the tooth enamel, but can cause sensitivity to teeth that is temporary. Some contend that they may be harmful if used for a long time and could turn the teeth bluish permanently. Some others feel that the teeth turn brittle if used often.
It is to be understood that most teeth whitening products involve the application of bleach that could make it unsuitable for people that have gum disorders and extreme sensitivity. However these people could benefit with having their gums treated first to make them healthy for application of whitening strips. Those having extreme sensitivity conditions could benefit from using products that are specialized designed for such users. These whitening strips can be used for a shorter period and have lower strength whiteners.