Advertisement

What are chemical sunscreens?

Dr. Ellen Marmur, MD
Dermatology

These are chemical ingredients that filter either UVB or UVA radiation. Instead of creating a physical block that deflects ultraviolet rays, they absorb the sun's light energy and convert it safely into thermal (heat) energy on top of the skin, which is then released. A primary scientific premise is that "energy is constant." It can be changed into different forms, like vapor changing to water, then changing to ice, but it's never really gone. So chemical sunscreens don't absorb the UV radiation as much as convert it into something benign (heat) that dissipates from the surface of your skin before it's able to reach the collagen in the dermis and the DNA in your cells. Chemical filters intercept that radiation and transform it into something much less dangerous.

The problem is that this photochemical reaction uses up sunscreen. Imagine that each chemical sunscreen molecule gets zapped and disappears the second it gets hit by a photon and converts to heat. Rather than wearing off, it is actually used up, like gasoline used by a car or food consumed by your body. That's why it must be reapplied. The more sun you are getting, the faster sunscreen is used up or breaks down.

Simple Skin Beauty: Every Woman's Guide to a Lifetime of Healthy, Gorgeous Skin

More About this Book

Simple Skin Beauty: Every Woman's Guide to a Lifetime of Healthy, Gorgeous Skin

What if a leading dermatologist just happened to be your best friend and you could ask her anything? DR. ELLEN MARMUR, a world-renowned New York City dermatologist, answers all your questions with...

Continue Learning about Sunburn Prevention

The New Science of Sun Protection
The New Science of Sun Protection
Got a love-hate relationship with your sunscreen? You’re not alone. We plunk down nearly $400 million a year on sun-care products in bottles, cans, tu...
Read More
How can I protect my lips in the sun?
Dr. Mehmet Oz, MDDr. Mehmet Oz, MD
Choose a lip balm with a sun protection factor (SPF) of at least 15. When using any sunscreen pr...
More Answers
What is the UV index?
Univ. of Nev. School of Medicine, Family MedicineUniv. of Nev. School of Medicine, Family Medicine
The UV (ultraviolet) index is a measure of the level of UV radiation from the sun. The values of the...
More Answers
How Much Sunscreen Should I Wear Every Day?
How Much Sunscreen Should I Wear Every Day?

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.