We asked Catherine Orentreich, M.D., a dermatologist affiliated with the New York University School of Medicine, to wade through the hype on summer skin-care products.
Q. What’s the difference between “sunscreen” and “sunblock,” and “water-resistant” and “waterproof”?
A. Sunscreen absorbs the sun’s damaging rays from within the skin; sunblock acts as a physical barrier to the sun by reflecting rays. Water-resistant products last 40 minutes in the water, whereas waterproof products last 80 minutes. (But you should always reapply the product after a dip, as you will probably towel much of it off.)
Q. Does makeup with SPF protect me as well as a sunscreen with the same SPF?
A. No. Makeup and moisturizers that contain SPF (even as high as 15) won’t protect you as thoroughly as a true sunscreen because the concentration of sun protection isn’t as potent. Combos protect against average daily UV exposure, not exposure to direct sunlight for an extended period of time.
Q. I’ve heard that any SPF higher than 15 will protect you the same amount as one labeled SPF 15. Is this true?
A. No. Sunscreens with an SPF higher than 15 protect skin from the sun’s harmful rays even longer. I usually recommend sunscreens with SPF 30 (or higher), especially for patients with fair skin.