...or magnesium hydroxide. Several years ago I read that this is a good mask for folks with acne, etc. I think the information might have been in the Paula Begoun book. Recently, I came across a bottle in my closet and have been experimenting with it overnight with some pretty good results. Maybe it's just the absorption of oil that is helping, since I also have seb derm. Some people apparently keep it on briefly before washing it off. Has anyone else tried it?