A few of my most recent #mythbustermonday posts have focused on two incredibly common sunscreen myths I hear from patients on a regular basis. As a dermatologist and avid sunscreen user, my job is to set the record straight, so let’s dive right in:
“Why do I need sunscreen during the week? I go straight from my house to my car to work and back again…”
Here’s one reason why: While UVB rays (burning rays) are blocked by window glass, UVA (aging rays) are not. And though it’s true that many new cars and buildings have UVA filters on their windows, most older public transit and offices, stores, and homes do not. Cumulative exposure through window glass has been clinically shown to cause signs of sun damage, like wrinkles, as in the published study by Clinical Interventions in Aging. Need visual proof? The image indicated here is of a 69 year old truck driver with marked unilateral sun damage on his driving side. The picture was so startling it spread across the lay media after publication in the New England Journal of Medicine in 2012.
“Does SPF 100 mean you can apply once and then forget about reapplying?”
A resounding NO! In a new JAAD article (pictured), research showed that one day use of SPF 100 reduced sunburn more than SPF 50. Not surprising since ‘SPF’ measures protection against UVB rays a.k.a the burning rays. The caveat is that it doesn’t measure protection from UVA a.k.a the aging rays and the ones responsible for the long-term sun damage discussed in my earlier post (see above). REMEMBER, wearing SPF 100 doesn’t mean you apply and forget. If you do, you may just be allowing yourself to be out longer without burning while you get more deep photodamage. To get broad-spectrum coverage with any product, apply well and apply often! My analogy – driving a car with all the safety bells and whistles doesn’t mean you can drive 90mph on an icy road. So feel free to buy high (SPF), but don’t forget to reapply!