Speaking of melanoma (yesterday’s blog), it’s time for another review about the basics of sunscreens. Which one is the best? Sprays are so fast and convenient- but do they work? Which ingredients matter?
Let’s start with SPF. What does it mean? Sun Protection Factor is a measure of a sunscreen’s ability to protect the wearer against UV radiation from UVB. Note that the sun produces both UVA and UVB, and BOTH cause damage that can lead to skin cancers. Right now, though, the SPF only addresses the UVB protection. So, SPF means that compared to bare skin, the sunscreen keeps you from burning X times longer. If it takes you a half hour to turn red with bare skin, a sunscreen with an SPF of 30 should in theory keep you from burning 30 times longer, which would be 900 minutes- 15 hours. Unfortunately, no sunscreen stays fully effective beyond two hours without re-application. Additionally, sunscreens with an SPF of 15 block roughly 93% of UVB rays, SPF 30 ~ 97%, and SPF 50 is 98%. Therefore, even with perfect application, no sunscreen blocks all UVB rays, and many block no UVA rays.
How much should you use to be effective? Surprise- would you believe it takes about an OUNCE (picture a shot glass), and that same amount should be reapplied every two hours. This means you will use roughly half of an 8 ounce bottle on ONE PERSON during a full day outdoors. (And no, I don’t own stock or have financial interests in sunscreens.)
Which ingredients are important? Most dermatologists recommend combining the physical barrier ingredients that protect against the deep penetrating UVA rays, such as ZINC OXIDE & TITANIUM DIOXIDE (the ones that leave the white residue) along with the chemical barrier agents known to block UVBs, such as PABA, salicylates, cinnamates and benzophenones. Since nearly all sunscreens contain mixes of the chemical barriers, I grab a tube or bottle and scan to be sure it also lists either zinc oxide or titanium dioxide as well. Note that some people are sensitive to PABA or other ingredients, and may do best with purely barrier sunscreens and clothing (such as surf shirts.)
Back to the sprays…they are not my first choice. Why? Few have either zinc oxide or titanium dioxide, and those that do are very expensive and have these minerals broken down into “nanoparticles” to allow them to be in a light enough liquid to spray. In the medical literature, some debate exists as to whether these nano-sized minerals can potentially cause cancer, which is of course, the opposite of our intent. Regardless of these issues, probably the biggest issue with sprays is that people use TINY portions- picture that less than 10 second total body spray- and so they are not obtaining anywhere near the listed SPF. Would I prefer that over skipping sunscreen all together? Yes…which means I do keep some on hand.
What do I usually buy? Our family likes Banana Boat’s “Baby” lotion. To it’s credit, my kids complain that their skin is “way too white” because I never let them tan. I take that as a compliment! Probably more importantly, for extended sun exposure we all use swim shirts, and try to consistently wear hats and sunglasses.
BOTTOM LINE: Get a sunscreen that contains both chemical and barrier agents (think titanium dioxide) and realize an 8 oz tube should be used up by a family of four in ONE morning OR afternoon since each person needs ONE OZ every TWO HOURS.