Marmur Medical Blog

Putting the SPF-y (pronounced “spiffy”) back into Sunscreen

Despite my mixed background, half Chinese and half Hungarian (of the gypsy variety), I have been dealt a rather, for lack of a better term, “absent” complexion. My skin has been compared to death warmed over, ruined several great family photos due to its photoluminescent properties, and said to be like that of the vampires from Twilight as it reflects the summer sun (cruel, I know). But, despite all the teasing I still maintain my “Snow White” complexion for both its look and the fact that it means I’m not undergoing unnecessary sun damage to my skin. Coming from the west coast of British Columbia, where the sun doesn’t shine for 10 months of the year, I’ve never had a problem with sun care. Since summer in New York City is clearly on its way, and the sun will definitely be shining in all its glory, I think it’s time for a little sun-protection education. So, what is SPF? What does it mean, what does it indicate, and how do I properly use this scale of sun protection?

SPF means “sun protection factor” and is an experimentally determined value obtained by exposing human subjects to a light spectrum mimicking sun at its most potent (i.e. noon). The subjects are divided into two groups – one wears sunscreen and the other does not. The length of time under the light spectrum that induces redness in the sunscreen-protected skin divided by the amount of light that induces redness in unprotected skin is the calculation used to determine SPF. In simpler terms, SPF is the measure of time it would take to sunburn if you are not wearing sunscreen as opposed to wearing sunscreen. For example, a sunscreen with an SPF of 30 should technically protect you for 30 times longer than without sunscreen application.

However, just to make protecting against the sun a little bit more difficult, SPF is really only a rating of UVB protection, the radiation that causes superficial skin damage (i.e. sunburns). Now, harkening back to the days of high-school science, we must remember that “sun light” (a.k.a. radiation) is really composed of both UVA and UVB (plus a whole slew of other things that are less consequential to our skin health). UVA radiation has been attributed with causing deeper skin damage. Unfortunately, at this point, there is no uniform measure of UVA absorption. So as confident as you can be that your broad-spectrum sunscreen has been scientifically tested for UVB protection, you can be as skeptical about its UVA defense.

Now that we have a working definition for SPF, let’s throw in the curve ball. Hypothetically speaking it would make sense that a sunscreen rated SPF 30 would cover a period twice as long as a sunscreen rated SPF 15. With this reasoning, I would like to buy a sunscreen with an SPF rating of a million please. But it just ain’t so! Logic of this magnitude would make it too easy for the consumer to buy the right product the first time around. Not only does SPF relate to how long it takes to manifest a sunburn if protected with said sunscreen, it also can relate to the amount of UVB radiation “deflected”. A sunscreen with SPF 15 will block anywhere from 92-94% of UVB radiation, SPF 30 will block 97% and SPF 45 will block 98%. This is a slightly less satisfying statistic. No matter how high a sunscreen’s SPF rating is, it will never fully protect you from the sun’s radiation.

But before you just give up and stop reading right now, there is also good news. With the proper application AND reapplication of sunscreen (no matter the SPF), along with appropriate sun protective clothing (hats, sheer coverings overlaying clothing that exposes skin etc.), one has a much better chance of surviving the summer sans burns or sun damage (skin cancer’s best friends), but still cultivate a “sun-kissed” glow (your ultimate sunbathing goal). Sunscreen should be applied indoors before venturing outside and as a general rule SPF 30 sunscreen should be reapplied every one to two hours (adjust from there if necessary, but I would recommend that no matter how high the SPF rating on your sunscreen, one shouldn’t wait beyond two hours to reapply). In addition, if entering a swimming pool, lake or ocean will be part of your sun-loving activities, the application of sunscreen should occur before and after entering water to ensure maximal protection.

Understanding the importance and meaning of SPF is a significant part of sun safety. Being armed with new knowledge has actually allowed me to spend a more relaxing and enjoyable time in the sun because I am not constantly worried about acquiring irreversible skin damage. So go out there, enjoy the glorious weather, and remember to never be too far away from your closest summer friend . . . not the mojito you are all probably imagining right now, but your most SPF-tastic sunscreen!

NOTE #1: Though the onset of summer prompted me to write this article, it does not mean that sunscreen is only warranted during the summer months. Even during the winter months when the sun is shining, the UV index is still high enough to merit the application of sunscreen. And just to make you even more vigilant about everyday sunscreen application, clouds do not stop the sun’s strength. In fact, 50% of the sun’s radiation is still penetrating to the Earth’s surface (incentive to wear sunscreen on a cloudy day)!

NOTE #2: Your lips are just as important and just as damageable as the rest of your skin. Treat them kindly and apply an SPF containing balm before glossing up!

Written by:
Margit Lai Wun Juhasz
Mount Sinai Medical Student