 One problem is that kids and their parents may not realize that some of these viral beauty products include active ingredients, such as chemical exfoliants known as AHAs and BHAs that help remove dead skin cells and oil. While those ingredients can be appropriate for teens with oily skin, Cheng says they're too harsh for the thinner skin of pre-teens. Their skin barrier can be compromised more easily. Their skin's more sensitive. Their skin's not as robust. And so any of these products can...