Teeth sensitivity is a common side effect of teeth whitening. However, the good news is that it is usually only temporary and should go away within a few days. There are a few things you can do to help minimize the discomfort, such as using a sensitive toothpaste or taking ibuprofen before the whitening treatment. If the sensitivity persists for more than a few days, however, it's best to consult with your dentist to see if there is another underlying issue.