Choosing sunscreens has become just a little more confusing recently with the introduction of high or very high, SPF sunscreens. I’m talking about SPF’s of 80, 90 or 100 and even 110, and I’m going to tell you why I don’t believe that these very high SPF sunscreens add anything to real, practical sun protection. First of all, sunscreens with an SPF of 15 give you 88% protection from all the burning UVB rays, 30 gives you 95% protection, 60 gives you 99% protection and once you’re up past 60 whether it’s 80, 90 or 110 you’re not getting any real additional protection from the sun. Now part of this, “numbers game” is being driven by consumer demand because consumers mistakenly think that an SPF at a certain point, if a little is good, more is always better. Well as you’ve seen, once you get passed 60 you’re not getting any additional protection and quite frankly, when you go from 95% protection to 99% protection, I’m not sure what that extra 4% translates to in terms of practical protection of sunburn or skin cancer. But I do know that as we go up in SPF usually the thickness or the viscosity or what I like to call the “goopiness” of the sunscreen, increases. And as that thickness or “goopiness” increases your much less apt to reapply the sunscreen during the day and the only way you can get the real SPF value in any of these is to reapply it frequently, after you sweat, after you swim, as we’ve discussed in other episodes. So there are some high SPF sunscreens that are made today that aren’t that thick but by and large, they are fairly viscous, that again discourages people from reapplying them. Lastly, when you have a very high number SPF like 110, it suggests to people that they don’t need to reapply that sunscreen. That’s a false sense of security because again, to get the full SPF value, regardless of what the number is, you’ve got to reapply it frequently. Now, to be fair and balanced, there may be one redeeming value to very high SPF sunscreens; the reason that most sunscreens fail is because people just don’t put enough on, so if you need an ounce to cover your whole body when you’re in a bathing suit, a lot of people don’t use that amount and when they don’t, the SPF value falls dramatically. Actually, to the square root of the SPF, which means a 15 becomes a 4, a 50 becomes a 7 and a 100 becomes a 10. Well, if a 100 becomes a 10, with a real SPF of ten, your still getting a reasonable amount of protection. But I’m going to maintain my position, that I recommend for all my patients every day, use an SPF of between 15 and 30 with UVA protection.
This is a bit off topic, but can you apply moisturizer with a retinoid medication at night? I've been using differin 0.3%, and my skin gets dry if i apply it daily. However, I want to keep using it frequently because it seems to be working.