I get asked three questions all the time. What sunscreen should I buy? What SPF should I use? Are sunscreens safe?
Before I address these questions, a little background on sunscreens will be helpful. There are two types of sunscreens: chemical blockers and physical blockers. Chemical blockers absorb UV radiation and then become inactive. Physical blockers (zinc oxide and titanium dioxide) reflect and scatter the UV radiation before it gets to your skin.
There are pros and cons to each type. Chemical sunscreens usually go on easier and feel nicer on your skin while physical blockers tend to be a little thicker and go on white. Chemical blockers can cause an allergic reaction and physical blockers do not. Physical blockers last as long as they are on your skin, while chemical blockers have a shorter period of effectiveness. Both types of sunscreens block UV radiation (UVR).
There are two types of UV radiation, UVB and UVA. Protecting yourself from both types is important. Physical blockers protect against both UVA and UVB. Chemical blockers all block UVB and have varying levels of UVA protection.
Why do dermatologists care so much about protecting your skin from UV radiation? UV radiation is a known carcinogen for skin cells and causes abnormal linkages and structural changes in your DNA. Indeed, sunburns are not caused by heat from the sun’s rays but by your body’s response to damage in your skin’s DNA.
Now, let’s answer the questions. The sunscreen you should buy is the one you will use regularly. If you polled all of the dermatologists in our group, you would get many different answers as to our individual preferred sunscreen brand. All of the sunscreens have similar ingredients. The differences lie in the other ingredients, known as the vehicle. Find a sunscreen you like that has both chemical and physical blockers and use it.
As far as SPF is concerned, you should use a sunscreen with at least a 30 SPF. The law of diminishing returns definitely comes into play with increased SPF. A 30 SPF sunscreen blocks 97 percent of UVR. A 50 SPF sunscreen blocks 98 percent of UVR. A 100 SPF sunscreen blocks 99 percent of UVR. A 1,000 SPF, if it existed, would block 99.9 percent of UVR. As a comparison, a white t-shirt, SPF 7, blocks roughly 85 percent of UVR. If this t-shirt gets wet, the SPF drops to 3 and it now blocks 67 percent of UVR.
The safety of sunscreens has come to the forefront of late and usually focuses on two questions: the safety of chemical sunscreens after they have been broken down by UV radiation and the safety of micronized zinc and titanium. I don’t want to minimize anyone’s health concerns, but there are no scientific studies to date definitively linking sunscreen to increased cancer rates or systemic toxicity. On the other hand, there are numerous studies linking sunscreen use to decreased rates of melanoma, basal cell carcinoma and squamous cell carcinoma.
Do yourself a favor and wear a sunscreen. Apply it every two hours and immediately after sweating or swimming and you should be able to safely enjoy an active outdoor lifestyle. FBN
Dr. Jordan Miller, M.D., FAAD, is a dermatologist at the Northern Arizona Dermatology Center.