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The Secrets of Sunscreen · MIT - Conversations with MIT Health

• 0:02
  Emily (Host): We've had a very cold winter here in New England, but
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  spring is right around the corner and before you know it, we'll be outside.
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  soaking up that precious New England sunshine.
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  That's why on this episode of Office Hours with MIT Health, we're tackling
• 0:15
  community questions about sun protection.
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  I'm your host, Emily Wade, and today I'm welcoming our expert
• 0:22
  for all things skin related.
• 0:25
  Dermatologist.
• 0:29
  David Li, MD: Thank you so much for having me.
• 0:30
  I'm very happy to be here.
• 0:31
  Emily (Host): Great.
• 0:32
  Before we jump in to our question, I just wanna do a quick note.
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  The info in this podcast is for general educational purposes only,
• 0:41
  and it's not a substitute for medical advice, diagnosis, or treatment.
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  So David, I'm gonna get right to our question from one
• 0:49
  of our community members.
• 0:51
  Dear Office hours, I'm a redhead and I get sunburns very easily.
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  For that reason, I always buy the highest SPF sunscreen I can find.
• 0:59
  But SPF 100 costs a lot more than SPF 50.
• 1:03
  Do higher numbers really provide extra protection or at least
• 1:06
  enough extra protection to make them worth the much higher cost.
• 1:11
  David Li, MD: Emily, that's a great question.
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  And it's one that we oftentimes get asked in clinic.
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  so the short answer is, yes, the higher SPFs do offer more, UV protection, right?
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  So take a step back.
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  SPS stands for some protection factor.
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  so as an example.
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  Right.
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  We always see things that are s SPF 15 s, PF, 30 SPF, 50 and s pf 100.
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  So s pf 50 blocks, about 93% of UV rays.
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  SPF 30 gets about 97%.
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  And then as you go up more, the curve really starts to flatten.
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  So at SPF 50, you get about 98%, protection.
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  And then, You know, the jump from 50 to a hundred only increases that by
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  one more percentage point to about 99%.
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  Emily (Host): So if I'm hearing you right, it sounds like the difference between s
• 1:59
  pf 30 and SPF one hundreds, only about 2%.
• 2:03
  That's, pretty small for such a big price jump.
• 2:06
  David Li, MD: That's exactly right.
• 2:07
  So, you know, based on the math, a lot of people might ask like, why even bother?
• 2:11
  Like, why not just settle for like SBF 30 where you're kind of, getting basically
• 2:15
  all you need in terms of the protection.
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  Emily (Host): but there has to be a catch, right?
• 2:19
  there's always a catch,
• 2:22
  David Li, MD: A a, a little bit, right?
• 2:24
  A little bit.
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  I think there are instances where, it is worth it shelling out for the additional
• 2:29
  SPF 50 or SPFA hundred even at times.
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  especially for those like our redheaded listener who, essentially what we
• 2:37
  call is Fitzpatrick skin Type one.
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  Essentially you go out into the sun And then you like, don't tan at all.
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  You just like immediately burn.
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  and I think the instance that makes it more reasonable to get
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  something like the SPF a hundred is.
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  is having to do with human behavior, right?
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  So those SPF values are largely determined in like perfect lab
• 2:56
  settings, perfect conditions.
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  and they're actually based off of applying about two milligrams of
• 3:01
  sunscreen per square centimeter, of skin.
• 3:05
  Emily (Host): So how much is that in like real-world terms?
• 3:08
  David Li, MD: that's about like one eighth of a cup or approximately a shot class
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  full of sunscreen for the average person.
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  But we know that in most cases we are definitely not applying
• 3:16
  that much onto our skin.
• 3:18
  Emily (Host): So This is like a lot of sunscreen.
• 3:23
  I, um, I definitely have a feeling most people are not putting this much on.
• 3:28
  on top of that.
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  I'm assuming This is not the only mistake that gets made with sunscreen.
• 3:33
  I.
• 3:34
  David Li, MD: Yeah, absolutely.
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  I mean, there are a ton.
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  I think most commonly we tell patient's that they typically need
• 3:39
  to reapply sunscreen every two hours.
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  I mean.
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  you're not doing a whole lot, the every two hours thing might be a bit much.
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  but let's say you know, you're going, swimming, or you're jumping into the
• 3:49
  pool, or you're sweating a lot, you may actually even need to, reapply more
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  frequently than every two hours because the process of sweating the process
• 3:56
  of going into the water actually.
• 3:58
  Gets rid of a lot of the useful, efficacious sunscreen
• 4:00
  that's currently on the skin.
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  But as a rule of thumb, we tell people every two to three
• 4:04
  hours reapply the sunscreen.
• 4:07
  so, between applying too little and not applying often enough, I guess
• 4:11
  the actual protection you're getting is far less than you might think.
• 4:13
  Emily (Host): okay, so This is where the higher SPF is
• 4:16
  gonna make the difference, I'm
• 4:19
  David Li, MD: A hundred percent.
• 4:20
  Yeah.
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  So, like our listener, that extra couple percentage points of UV protection
• 4:24
  might actually matter because it's more of like a, a safety net for them.
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  I will say though, if applying SPF 100 makes you look very, You know,
• 4:33
  white cast and pasty and you're not gonna wear the sunscreen, then I would
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  much rather have the patient wear something that's like an S pf 30.
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  So the best sunscreen is gonna be one that they're actually going
• 4:43
  to use on a day-to-day basis
• 4:45
  Emily (Host): that's very good point.
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  Well, and now we at least know how much you, you should be putting on.
• 4:51
  okay.
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  So.
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  That's a great answer for our redhead out there who, um, I'm assuming they're maybe
• 4:58
  a Sloan listener since they wanted us to do some cost benefit analysis there.
• 5:03
  David, would you be interested in any lightning round of our shorter
• 5:07
  questions that we've had come in?
• 5:09
  David Li, MD: Sure, let's do it.
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  Emily (Host): Okay.
• 5:12
  What ingredients should I look for in sunscreen?
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  I want something that's effective, but that's also safe
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  for me And the environment.
• 5:19
  David Li, MD: that's a good question.
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  So I tend to think of it in, into like two buckets, right?
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  So we have, mineral sunscreens, And then we have chemical sunscreens.
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  So mineral sunscreens contain minerals like zinc oxide, titanium dioxide, I So
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  Those are, Essentially they're, they're like minerals that sit on top of the
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  skin as you apply, and they work from the moment that you apply the sunscreen.
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  So you apply it, you go outside.
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  It works just like that.
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  on the other hand, you have things like chemical sunscreens, which can contain
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  a variety of different ingredients.
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  And those actually take about 15 minutes or so to work, right?
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  They have to, get absorbed into the.
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  Top layer of the skin, And then they work by actually absorbing
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  the UV And then converting it into heat that then, You kind of gets
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  released from the surface of the skin.
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  so the big difference here is that the first bucket of the mineral sunscreen does
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  not get absorbed into your skin at all.
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  The second, which is the chemical sunscreens, they've done some studies,
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  I think in the last couple of years.
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  there's one that was published in jama, which showed that if you actually apply
• 6:15
  enough of the chemical sunscreen onto your body, it has to be like a, a ton.
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  You will find that it, there will be enough of the chemical sunscreens which
• 6:23
  go into the bloodstream, the serum, and it's measurable and detectable.
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  What that means clinically in terms of safety.
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  It's really, we really don't know.
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  so, I guess the other thing is that.
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  Mineral sunscreens are generally safer for, the marine life and reefs.
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  I think that's what the question is getting at.
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  so between those two, you know, I, I personally am.
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  I'm fine with either mineral or chemical sunscreens based on the data.
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  It doesn't show that one is necessarily more dangerous to you than the
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  other, but I think if you're very environmentally conscious and you
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  wanted to avoid, things that could be bad for the reef and marine life, I'd
• 7:01
  probably go with a mineral sunscreen.
• 7:03
  Emily (Host): That makes sense.
• 7:04
  alright, here's another quick fire question.
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  spray versus lotion.
• 7:09
  David Li, MD: I would definitely recommend a lotion.
• 7:13
  I think a spray is far less consistent.
• 7:16
  You're not sure how far to spray, you're not sure how much to spray, And then, how
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  much of it really is getting onto the skin versus being like blown into the wind.
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  You know, like we're all used to that experience, like growing
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  up by the beach or the pool.
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  Like we smell that kind of sunscreen spray being, blown down wind.
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  We're like, oh my God, what is that?
• 7:33
  Emily (Host): Yeah.
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  It's like a cloud of coconut smell.
• 7:37
  David Li, MD: yeah, yeah, yeah, yeah.
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  Exactly.
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  Yep.
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  Yep.
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  So, so for that reason, I, I personally am much more a proponent for the lotion
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  version, you know, where you're kind of getting a better sense of how much
• 7:48
  is actually going onto to your skin.
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  there's less, doubt about it.
• 7:52
  Emily (Host): Okay.
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  We've got one more lightning round question.
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  I have darker skin and I don't burn easily.
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  Do I still need sunscreen?
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  And if so, can you recommend something that won't leave that white or ashy cast?
• 8:06
  So I guess not the super high SPF.
• 8:08
  Huh?
• 8:10
  David Li, MD: Yeah.
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  short answer is yes, and I think this question is one that was, you
• 8:14
  know, previously, debated in the last, I would say, five, 10 years
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  or So, It is like, do patient's with darker skin actually need sunscreen?
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  so even though patient's with darker skin have more natural protection from.
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  Essentially getting a sunburn UV radiation is still happening.
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  It still can cause sun damage, and it does increase the risks of certain types of
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  skin cancers that are, you driven by uv.
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  in addition to this, patient's with more pigmented.
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  Skin are, actually more prone to things like hyperpigmentation or darkening of
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  the skin, as well as, conditions like melasma, which is that kind of, you know,
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  hyperpigmentation around the face that we oftentimes see in some patient's, which
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  is partly worsened by, sunlight, but driven largely by other factors as well.
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  so the question also, was asking how do we avoid that kind of white
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  cast, is the perfect situation to talk about, I think tinted sunscreens.
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  So tinted sunscreens protect from the UV spectrum in addition
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  to the visible spectrum.
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  they do that by containing something called iron oxide and, and It's very good.
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  tinted sunscreens are fantastic and I recommend them for patient's with,
• 9:20
  light brown, kind of, uh, a little bit more pigmented skin where if you apply
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  something that's a high SPF 50 or above, you'll look like you have that white cast.
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  And the tinted sunscreens really help to prevent that from happening.
• 9:31
  Emily (Host): That is really great advice.
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  I, even me, I, I've definitely looked like a mime before putting on that
• 9:40
  kind of like high SPF sunscreen.
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  So I, think that's really helpful advice.
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  All So, it sounds like.
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  We have learned that if you are going to use a lower SPF, you might want to think
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  about using a higher amount of sunscreen.
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  and we've learned a lot about different options of sunscreens that you can
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  use and different applications.
• 10:06
  Dr.
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  Lee, thanks so much for being here and clearing up the
• 10:09
  confusion around sunscreen today.
• 10:12
  David Li, MD: Absolutely my pleasure.
• 10:13
  You know, I hope today's conversation is somewhat helpful for listeners,
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  when they're thinking about how best to protect their skin, especially as we get
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  into the, uh, spring, sunny or weather.
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  I would like to say that, you know, whether you have a mole,
• 10:23
  you'd like to get checked out or struggling with acne, hair loss.
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  skin growths or even warts, or you just want some expert advice on, on your skin.
• 10:31
  our dermatology team is located at MIT Health and we're more than happy to help.
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  you can make an appointment online and you don't need a referral.
• 10:39
  Emily (Host): That is so awesome.
• 10:41
  I actually, that's good.
• 10:42
  A reminder, I think I need to make an appointment myself, Thanks for a great
• 10:46
  episode of Office Hours with MIT Health.
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  Thanks for tuning in, and if you have a question, stop by health.mit.edu/thrive
• 10:56
  and submit your question for one of our great clinicians to answer.
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  Take care.