The whitestrips definately work. I noticed a significant difference within 3 days. After completing the pack, I went through a 2nd treatment (as instuctions recommend for optimum results), but, I really don't think the 2nd pack made much difference.
I will buy these again in another 6-9mths. The only cons are that the bottom strips kept bunching up and sliding around...I was so paranoid about swallowing this stuff--which I'm sure causes cancer or stunts growth or something--that I drooled and spit a lot! LOL
But, we must suffer for beauty sometimes...and this was worth the "suffering"!
