ASK THE EXPERT: How much sunscreen should I be using on my face and body?

By Elizabeth K. Hale, MD

Dr. Hale is clinical associate professor of dermatology at the New York University School of Medicine. Dr. Hale is a member of the American Academy of Dermatology, American Society of Dermatologic Surgery, American College of Mohs Surgery, American Society of Lasers in Medicine and Surgery, and the New York Facial Plastic Surgery Society. She practices dermatology at Laser & Skin Surgery Center of NY, and lectures extensively on the prevention and treatment of skin cancer.

Q: Whenever I apply sunscreen, it makes my skin look white. Am I applying too much? How much sunscreen should I be using on my face and body? 

A: Some common sunscreen ingredients, including the physical (or mineral) blockers zinc oxide and titanium dioxide, can make the skin look white, at least until the product is adequately absorbed. These sunscreens physically “block” skin from the sun, and they have several advantages. They tend to work immediately, unlike chemical sunscreens, which need to be absorbed before they work effectively. Titanium dioxide and zinc oxide also screen out a wide range of the sun’s cancer-causing ultraviolet A (UVA) and B (UVB) radiation — zinc oxide, in particular, effectively blocks all parts of the UV spectrum. Protection from both UVA and UVB is necessary, and some chemical sunscreens don’t provide comparably broad- spectrum defense. Also, physical blockers are preferred for young children’s sensitive skin, and for people who may have concerns about certain ingredients in chemical sunscreens.

In general, the higher the concentration of a physical blocking ingredient, the more effective a sunscreen is (some concentrations of zinc oxide and titanium dioxide are over 10 percent), but there are several ways to minimize the whitish appearance. You could choose a micronized formulation, which has smaller-sized, more easily absorbed sunscreen particles. Another option is a tinted sunscreen that matches your skin color. Or you could use a sunscreen with chemical blockers in lieu of, or in combination with, physical blockers. The chemical blocker avobenzone, for example, has a long track record of safety and tolerability, and leaves no telltale white cast.

It is very unlikely that you’re applying too much sunscreen — most people don’t apply enough, which is why undesirable sunburns and tanning can occur despite sunscreen application. To achieve the Sun Protection Factor (SPF, which protects against the sun’s UVB radiation) reflected on a bottle of sunscreen, you should use approximately two milligrams of sunscreen per square centimeter of skin. In practice, this means applying the equivalent of a shot glass (two tablespoons) of sunscreen to the exposed areas of the face and body – a nickel-sized dollop to the face alone. If you’re using a spray, apply until an even sheen appears on the skin. Remember that sunscreen needs to be reapplied every two hours, or more frequently after swimming, heavy perspiration, or toweling off. Also remember, no matter how much sunscreen you apply, the SPF should be 15 or higher for adequate protection – and ideally 30 or higher for extended time spent outdoors.

In addition to using sunscreen, seek shade whenever possible, and wear sun-protective clothing, broad-brimmed hats, and UV-blocking sunglasses.

Published in the Fall 2010 Edition of Sun & Skin News