Serving size: A nickel (near right). Purifying masks can clear up pimples and diminish the appearance of pores, but they quickly sap skin’s moisture if overused. For best results, target only oily areas—the T-zone, for example—and use the mask no more than once a week, says Jeannette Graf, a dermatologist in Great Neck, New York.
Serving size: A pea. Whether the formula is designed for combating blemishes or lightening dark patches, a pea-size amount will give you the benefits without irritating the surrounding skin.