What it is
Bentonite is a type of clay.
What it does
Bentonite is primarily used as an absorbent in cosmetics. Its ability to soak up excess oil and liquids makes it beneficial for those with oily skin.
In addition, Bentonite can be used as a bulking agent (a substance that can increase volume of solids or dilute them), to prevent the oil and water parts of a product from separating and to reduce the transparent appearance of some cosmetics.
Because of its absorbent properties, Bentonite can be drying for those with dry skin.