http://www.bellasugar.com/3370043.. a little more information there.
"This product should be shaken before use to represent the blending of the human and vampire worlds and applied repeatedly until lips are plumped, revitalized and the desired intensity of color has been reached."
So it was a pretty cool thing, makes your lips tingle, I didn't realize it was a plumper when I bought it but it definitely explains the sting. A friend sent me the link and I got it really without reading anything about it.
The stain color can go darker, as you read before, it can get really really red. So thats always a plus that you can personalize your color. Just be careful not to get it everywhere, like I did.
So the end product is pretty cool:) Love to all the Twilight fans out there!