This Review Title is Not Worth the Money, Acid Spray? and the content is: Despite exfoliation goes on uneven, staining darker towards the inside of the mouth than around the perimeter.  The spray appears to be some kind of acid; really made me wonder about what inevitably ended up inside my mouth.  The color lasted only about 5 hours..There are other information for this review, one is This reviewer did purchase it and the other is 2 people think this review is helpful.