Are you put off by the idea that tooth whitening might be painful? While it is true that some patients experience pain after whitening treatment, it helps to know why before you decide against whitening. If you take the right precautions before and after treatment, you can reduce or even stop after-whitening pain. Why Whitening Sometimes Hurts Not all patients experience pain during or after a whitening procedure. Under normal circumstances, you may experience some sensitivity afterwards, but that should last no longer than 48 hours.