University of Pennsylvania Health System

Penn Health and Wellness

Tuesday, August 26, 2014

How to Choose Your Sunscreen

It’s no secret that sunscreen offers the best protection against skin cancer next to staying out of the sun altogether or covering up with sun protective clothing. However, most people don’t realize that the kind of sunscreen we use is also important. Did you know there are two main kinds of sunscreen? Chemical sunscreen and physical sunscreen.

Chemical Sunscreen vs. Physical Sunscreen – What’s the Difference?

A sunscreen is a compound (or lotion) that uses agents to block, deflect or reflect the sun’s rays.

To be effective, we recommend that all sunscreens be liberally applied (at least one ounce for the entire body) to all exposed areas of the body, at least 15 minutes before going outside.

Chemical sunscreens use up to a dozen ingredients that, when applied, are absorbed in the top layer of skin. They react with the skin to absorb UV rays and convert them into energy before they can harm the skin.

Chemical sunscreens aren’t as thick as physical ones, so they are often used in sunscreens specifically made for the face as well as those found in spray bottles. Since chemical sunscreens need to be absorbed into the skin, they must be applied at least 20 to 30 minutes before heading outdoors.

Physical sunscreens, sometimes called “natural or mineral” sunscreens, include two ingredients: zinc oxide and titanium dioxide. Together, these ingredients sit on top of the skin and deflect or reflect the sun’s rays.

Think of physical sunscreens like a shield, while chemical sunscreens are absorbed into the skin. Both ingredients work well to protect from UVA and UVB (broad spectrum) rays. Since physical sunscreens are thicker, they can leave a white cast on the skin.

Which Sunscreen Is Right for You?

Those with sensitive skin, especially young children, should opt for a physical/mineral sunscreen since those ingredients are milder. Those with darker skin may opt for a chemical sunscreen, since they don’t leave a white cast.

According to plastic surgeon, Ivona Percec, MD, PhD, “A chemical sunscreen really just protects against UB – the burning rays. In two hours that’s degraded by the sun. The mineral block [physical sunscreen] is the much better block because it protects against both UVA and UVP.”

Both types of sunscreen provide adequate protection. Your personal preference may help you decide what type of sunscreen is right for you.

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