Teeth cleaning kit made my mouth really hurt, why?

I bought this pearl teeth kit yesterday that is supposed to make my teeth whiter - I'm getting braces in less than a month so I want my teeth to be nice and white. Anyways its just stuff you rub on your teeth, it kind of looks like toothpaste. I did that...

like 7 hours ago, and now my gums and teeth are hurting A LOT.

Could this be some sort of allergic reaction?

I looked around online, and it may be due to the amount of peroxide in the whitening product that can make sensitive teeth and gums hurt.

Some people experience no pain or sensitivity with their teeth. However, the majority of people will experience some kind on sensitivity either during and / or after the initial treatment. This is usually described by patients as sporadic sharp shooting pains coming from your teeth. This should settle down after approximately 48 hours. Your dentist may give you a special gel or mouse to apply to your teeth to help with the sensitivity. It is advisable to avoid and hot or cold food or drinks within the first 48 hours of your whitening treatment.

Just some FAQs that you can check out here:
http://www.fantasysm...
http://www.cosmeticd...

When I use white strips my teeth and gums are really sensitive and hurt for about a half hour later...