Why does bleaching my teeth hurt a lot?

Not really: If you have sensitivity of the roots of your teeth, it can be uncomfortable. Usually it is painless with a great outcome.

Hydration: The whitening ingredients work by liberating oxygen inside the porous areas of your teeth in effect they get "dried out". This signals the nerve inside that something may be wrong like a cavity because of the osmotic pressure change. Some people are more sensitive to this but fortunately it's temporary. Once the teeth rehydrate the pressure balances and the pain goes away!

3 reasons: If the sensitivity is severe, there may be the following reasons: 1. The carbamide peroxide concentration is excessive, or the exposure time is excessive; 2. There may be cavities or gum desease present; 3. You don't follow the instructions. Consult your dentist, he or she can certainly adjust your whitening regimento make it more comfortable. Good luck!