Understanding Sunscreen Ingredients And Which Ones You Need

Picking a sunscreen can be overwhelming. We’ll break down what to look for, and what ingredients matter.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Ira Flatow?

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• 0:16Speaker 01

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• 1:01Flora Lichtman?

  Hey, I'm Flora Lichtman, and this is Science Friday.

• 1:08Flora Lichtman?

  Today in the show, sunscreen, what to look for, and your burning sunscreen questions.

• 1:14Speaker 04

  Ultimately, the key thing is this to recognize is that this ultraviolet radiation, whether you're wearing sunscreen or not, is coming down on you. So you need to protect yourself from it.

• 1:27Flora Lichtman?

  It's officially summer, and that means a few of my favorite things: barbecues, beaches, and broiling under the sun. Which also means it's sunscreen season. But if you meander down the sunscreen aisle in the drugstore, you're confronted with so many choices: mineral, chemical, nano, non nano, UVA, UVB. What is the difference? What ingredients should you look out for? What belongs in the shopping basket, and what doesn't? Here to shine some light on some of those questions is Dr. Jonathan Unger, a dermatologist and medical director of the Waldman Melanoma and Skin Cancer Center at Mount Sinai here in New York. Welcome to Science Friday.

• 2:06Speaker 04

  Thank you for having me.

• 2:07Flora Lichtman?

  Okay, so let's break down first, sort of, you know, it's been drilled into our heads, the sun can cause damage. But what is actually causing damage? And how much do we know about that?

• 2:18Speaker 04

  So a tremendous amount of electromagnetic radiation travels from the sun down to our skin. There are many aspects of this sort of spectrum. They include visible light, that's how we see, but among those is also ultraviolet light. Ultraviolet light, we can't see, but it is quite damaging to our cells and specifically the DNA of our cells. We think of UV as three sort of sub-spectrums, there's UVA, UVB, and UVC. UVC is actually by far the most damaging and is often used to sterilize because it basically damages and kills all life. Fortunately for us, our atmosphere really eliminates that, but-

• 2:57Flora Lichtman?

  Thank you, atmosphere.

• 2:59Speaker 04

  Yes, exactly. But UVB and UVA do make it down to the surface of the earth and do hit our skin, and they do cause damage, different kinds of damage, but still, they are causing damage, and some of those, some of the damage, excuse me, can ultimately lead to the development of skin cancer.

• 3:16Flora Lichtman?

  And which one do we have to be most worried about, or both?

• 3:19Speaker 04

  So, we really need to be worried about both. UVB, that part of the spectrum is most responsible for the development of skin cancers, but UVA also does damage the skin, it's responsible for a lot of the aging processes that happen in the skin, which of course, many people are concerned about. So, they both are bad, but in slightly different ways.

• 3:38Flora Lichtman?

  You know, so I have young kids, and it was drilled into me by social media that I had to use mineral sunscreen on my little kids. Is there anything to that? What is the difference between mineral and chemical, and how do I pick between the two?

• 3:53Speaker 04

  So, that's a really good question, and I think something that probably confuses a lot of people, because between social media and other sources, there's a lot of confusing information out there. I like to always counsel my patients by saying, ultimately, the key thing is this to recognize, is that this ultraviolet radiation, whether you're wearing sunscreen or not, is coming down on you, so you need to protect yourself from it. When we talk about sunscreens, there are two classes of ingredients, although there are more than two. There are the physical sunscreens or the mineral sunscreens. Those in the United States are going to be zinc oxide or titanium dioxide.

• 4:25Flora Lichtman?

  That's the mineral.

• 4:26Speaker 04

  Correct. And then, the other ones are what we call chemical sunscreen, and sunscreens, and in the United States, there are 12 that are acceptable for use in sunscreens. There are more of them around the rest of the world, but in the US, there are 12 of them, and they all have unpronounceable names.

• 4:41Speaker 04

  So the mineral sunscreens work differently, though, which explains, in fact, why some people don't like to use them because they have this kind of whitish cast, right? The way that they work, physical blockers, is by blocking and reflecting light, right? The UV radiation hits these, the particles, and they get reflected. Along with the ultraviolet, which is not visible, they also reflect some visible light, hence the whitish appearance. Chemical sunscreens work differently. Their chemical structure allows them to absorb some of the ultraviolet radiation. That absorbed energy is then converted into heat, which is tiny amounts of heat, and that gets absorbed and dissipated in the skin. But because it's absorbing that and not reflecting the visible light, you don't see those.

• 5:20Flora Lichtman?

  But is there any truth to this idea that chemical is less safe for little kids than mineral?

• 5:27Speaker 04

  I would say the jury is still out. There is no strong, compelling data that says they are bad. And it's important to take a moment to say that sunscreen is considered an over-the-counter medication in the United States, so it's regulated by the FDA. Regulated strongly, which is why some sunscreens that are available abroad are not available here, or if they are, they're formulated differently. Because, as I said earlier, some sunscreen ingredients are not approved for use in the United States but are elsewhere. I always tell people this: when things are muddy, when the water is muddy, you have to do what you feel comfortable with. I would say some of this is muddy. What's not muddy is that UV radiation is bad, so you need to protect yourself from it. If you're someone who feels comfortable using chemical sunscreens, and I'll admit,

• 6:10Speaker 04

  I use both kinds personally, then you should use either one. If you have strong concerns that maybe the data and the science, as it bears out, will show that there are some problems with the chemical sunscreens, then I would say use the mineral ones. But what I don't think is a good solution here is to say, "Well, I don't want to use the mineral ones because they make me look like I'm wearing whitish makeup, and I don't want to use the chemical ones because I'm worried that they're going to have some sort of health issues down the road, so I'm not going to wear sunscreen." Because what many people don't realize necessarily is that the number-one, number-two, and number-five most common cancers in humans in the United States are all skin cancers, and at least in part, if not entirely, are caused by UV exposure.

• 6:53Ira Flatow?

  All right, let's go to the phones. A lot of people want to talk about it.

• 6:55Flora Lichtman?

  Should we try Liz in Wyoming?

• 6:56Ira Flatow?

  Go ahead. Hi, Liz. Hello. Hi there. Hi there, go ahead.

• 7:02Speaker 05

  Hi. My question is about sunscreen in makeup products. There is a ton of products out there that claim they have SPF and, you know, if you put it on under your makeup or after your makeup that it will help. But I wanted to know, how effective are those? You have to reapply them and what sort of the truth about makeup or products like that that include an SPF?

• 7:26Speaker 04

  So that's a really excellent question and one I think I get commonly asked in my practice. Mineral sunscreens predominantly work through the use of zinc or titanium oxides, right? They're powders that go into the makeup and I think initially they were probably incidentally there. There is no such thing as a sunscreen that lasts all day. In fact, again, going back to the idea that these are over the counter medications, they have instructions for use. For instance, how frequently you need to reapply. Some of them, for instance, have water resistance or not. I would say makeups are a little trickier because they don't contain those, they don't necessarily have it. So I tell people, if it's just for daily use, you're going to be in and out periodically for a few minutes at a time.

• 8:08Speaker 04

  If the UV index, which, you know, that's a new term I'm introducing here, but if the strength of the UV at that point in time is not very high, being a realist, I would say, fine, that's probably okay. But if you're going to be out for more extended periods or you're just being exposed to a lot of ultraviolet light, I would not just rely on makeup as the primary source of sun protection.

• 8:27Ira Flatow?

  I think I got Deborah in Pittsburgh there. Deborah, are you there?

• 8:30Speaker 06

  I am here, hello.

• 8:31Ira Flatow?

  Go ahead.

• 8:33Speaker 06

  Here's my question. I have a skin sensitivity to chlorine and so sometimes when I wear different sunscreens, I break out, especially on my face, my arms, my legs. But I don't know what ingredient or what products I should stay away from because I just never know which is going to react with my skin.

• 8:54Speaker 04

  So that's a really great, great point. I mean, sunscreens are pretty complicated for the most part. They have many, many, many ingredients and many people have sensitivities to a lot of different products, whether they're sunscreen ingredients themselves or all the other things that are in the creams or the lotions or the sprays and things like that. In dermatology, we do a certain type of testing called patch testing, which is allergy testing to isolate ingredients in these sorts of things and then to test and to help you to determine what you're specifically allergic to. And then, of course, once that's determined, then there are all these lists of products that are safe for you and ones that are not safe for you. So you can certainly find out more about patch testing with your dermatologist or find that and then they can help you to isolate those products. Otherwise, you're playing a very difficult guessing game.

• 9:44Flora Lichtman?

  We have to take a break. And when we come back, smuggling in foreign sunscreens and can sunscreen block you from getting your vitamin D?

• 9:54Speaker 04

  I always tell my patients, there are really two ways to get your vitamin D. One of them increases your risk of cancer. I'm not going to tell you which one, but you get to choose which one you want to use.

• 10:03Flora Lichtman?

  Stay with us.

• 10:09Ira Flatow?

  Hey, Ira here. You've probably heard me say many times that we are all in this together. We're so encouraged by those who have backed me up on this by stepping up to support Science Friday in the face of the current funding challenges. So thank you to everyone who has donated in the past month. It's clear that many of you value science and count on public media as we do. You are the driving force behind our work. Your support strengthens Science Friday, provides stability in these moments of volatility, and your support is more crucial now than ever. So if you haven't made a donation to help close the current funding gap, you can still

• 10:52Ira Flatow?

  make an impact by going to sciencefriday.com/donate. Any amount you can give helps to sustain Science Friday programming in this critical moment. Again, that's sciencefriday.com/donate, and thanks.

• 11:10Speaker 01

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• 11:45Flora Lichtman?

  Support for Science Friday comes from the William K. Boas Jr. Foundation.

• 11:54Flora Lichtman?

  Have there been any advances in sunscreen, like, in the last 20 years?

• 11:59Speaker 04

  That's a really good question, and the short answer is, in the United States, not really. It's been fairly static, although regulations and proposed regulations have sort of changed a bit. But really, 1999 is like when the last real set of guidance and rules, so far as they know, really came into effect. So that's both a good thing and a bad thing. The good thing is, this is not something that's changing every other minute and complicating an already complicated area. But, you know, I know that, for instance, the FDA is currently considering revised rules, but I think one of the challenges is they need more data, and that data is a little bit more difficult to come by.

• 12:33Flora Lichtman?

  Because no one's doing the studies, or?

• 12:35Speaker 04

  It depends who you ask. I think the FDA would argue that they have to request voluntary submission of data from the companies that make the sunscreens, and they've been a little slower to provide that.

• 12:45Ira Flatow?

  You know, what is the difference? When I go to the beach and I see the lifeguards, but they have this white nose. Are they putting on something different than I'm doing as a sunscreen?

• 12:56Speaker 04

  The sunscreen ingredient is the same, the concentration is different. In fact, what they're putting on their nose is the same thing as parents put on for diaper rashes, which is zinc oxide also. It's the same ingredient, it's just at a much higher concentration. And the reason it looks so white is, there's so much of it that it's just reflecting all that visible light back at you.

• 13:13Flora Lichtman?

  Is that SPF 100, then?

• 13:15Speaker 04

  Probably a billion, I would say.

• 13:17Ira Flatow?

  But that's the ultimate, right?

• 13:18Speaker 04

  Yes, exactly.

• 13:20Ira Flatow?

  Yeah, you don't want to put that all over.

• 13:21Flora Lichtman?

  What about, um, so you mentioned that in different countries, there are different ingredients. Do you have patients who, who smuggle in sunscreens, who have their favorite overseas brand, you know, like baby formula, we see, we see this too.

• 13:32Speaker 04

  I'll never name names, but the answer is absolutely. Um, I have many patients, for instance, um, there, where there is a particular brand of sunscreen that they love that's available in Europe, for instance, even in Canada. And it is available here, but it's because of those regulatory issues, they can't use both and they smuggle it in. I imagine if you bring us a tube or two for your own use, no one's going to say anything. If, if you have three suitcases filled with it, um, the customs, uh, officers might have a, might, might bring an issue because you can have it, I believe, but I don't know if you can sell it.

• 14:04Flora Lichtman?

  Let's go to the phones. Let's go to Laura in Corvallis. Hey, Laura.

• 14:08Speaker 05

  Hi, I'm wondering about, uh, vitamin D production. When you're using a sunscreen, do I use it a lot and I just concern, I use it year round?

• 14:18Speaker 04

  So.

• 14:18Flora Lichtman?

  And does it block, does it block the vitamin D production? Yeah.

• 14:21Speaker 04

  So that's a great question. If you look at the biology of the way that our body produces vitamin D, and I'll just note, it's the only vitamin that our body actually produces. Everything else you have to get from the diet and it's very hard from the sort of natural sources to get sufficient vitamin D. So we do rely on our skin to produce it and it is part of the UVB spectrum, which is the worst part of the sun's exposure from a skin cancer perspective and from a sunburn perspective. It's the same part of the spectrum that's responsible for the production of vitamin D. And so this is a, a question that I encounter very often because vitamin D is essential and many of my patients who use sunscreen regularly and consistently end up vitamin D deficient. The good news is we have many modern technologies that allow us to account for all kinds of things.

• 15:04Flora Lichtman?

  Like vitamins?

• 15:05Speaker 04

  For instance, vitamin supplementation. Vitamin D3 is extraordinarily inexpensive, is bioequivalent. So it's the same vitamin D and your body treats it exactly the same way. Um, if you take vitamin D2, your body's enzymes, unless you're deficient for some reason, is able to convert those. So I always tell my patients, there are really two ways to get your vitamin D. One of them increases the risk of cancer. I'm not going to tell you which one, but you get to choose which one you want to use.

• 15:30Flora Lichtman?

  Can you walk us through SPF? What is it? And how meaningful are the distinctions between 50 and 70? For example?

• 15:39Speaker 04

  Another very, very, very common question because there's a lot. Some people think of it as percents, which it is not. It's a some protective factor and it's a it's a scale that I believe has its roots in the idea of how much longer an equivalent exposure to UVB would take to result in a sunburn. So because they look for places on people's body that don't get sun, so there's no natural sort of tanning or anything like that. They used to use people's backsides and they would put it on one and put it on the other and start exposing you to ultraviolet B and see what the difference in terms of how much longer it would take to get a sunburn. I suspect they have more modern techniques for measuring that. But so SPF 30 and SPF 50 doesn't tell you one is two thirds longer the other.

• 16:23Speaker 04

  SPF 30 blocks about 96.8%. So let's say 97% of UVB when used properly. And that's really important. Right? You can put a tiny little drop for your whole body or you can put a huge amount. This goes sort of the question of what you're putting on your nose, right? When it looks so white. SPF 50 blocks 98%. SPF 100 blocks around 99%. It's interesting and just a complicated and already complicated topic is anything above SPF 50 is sort of is not regulated that that that number by the FDA. It's at least a 50, but it's sort of question of whether you trust the manufacturer that it's providing 70 or 90 in their labs.

• 17:03Ira Flatow?

  We're talking about sunscreen to protect your skin. What about your eyes? Should we be wearing those UV blocking sunglasses?

• 17:11Speaker 04

  Let's put it this way. The way we see is by the exposure to visible light that comes along with all that UV radiation. And there are certain types of ocular melanomas and against ample cancers that can be related to as well. So the answer is yes. I mean, we really all do need to be protecting the eyes like our skin are remarkable tissues that have the resilience and an ability to deal with it. But you can't put sunscreen on your eyes. You really shouldn't put sunscreen on your eyelids. So getting in the habit of wearing UV protective sunglasses is a good idea.

• 17:40Flora Lichtman?

  Let's go to the phones. Let's go to Brooke in Wisconsin.

• 17:44Flora Lichtman?

  Hi, Brooke.

• 17:44Speaker 05

  Hi. Hi. My daughter just turned six months today and I know now I can start using sunscreen and I'm wondering how often we should be reapplying it?

• 17:55Speaker 04

  So first of all, congratulations. And I will say that this is really important. Every sunscreen, in theory, could have slightly different instructions. So I always encourage people to read the label. It's a requirement of the FDA that, beyond, most sunscreens, it's every two hours except for exceptional circumstances. For instance, if you get in the water or you're very sweaty. I always encourage my patients to just err on the side of caution. If it's two hours, do it every hour and a half to hour and 45 minutes. To remind myself, especially if I'm spending long periods of time outside, I'll set a timer on my phone, actually. And when it goes off, I hit repeat, I apply sunscreen, and I just kind of do that throughout the day.

• 18:37Flora Lichtman?

  This is a very dermatologist thing to do.

• 18:39Speaker 04

  Yes, exactly. I was going to say, this may be too crazy for most, but otherwise, it's just easy to forget. And then, of course, if you're getting in the water, again, sunscreens are not waterproof. In fact, that labeling is no longer allowed in the United States. You're allowed to say water resistant up to 40 minutes or water resistant up to 80 minutes. But that's hard for people to even know, what am I doing? Okay, I was in the water for 35 minutes, so does that mean I don't have to reapply? Do I have to reapply to two hours? Do I have to reapply to 40 minutes? So my advice to people is if you've been in the water, if you're extremely sweaty, towel off, reapply, err on the side of caution with these things.

• 19:13Flora Lichtman?

  In the 30 seconds we have left, tips for shopping? What should I look for? What should I avoid?

• 19:19Speaker 04

  You want to look for a sunscreen that has at least an SPF 30, although I would say the higher the better. I'm a big advocate of that. The label should say broad spectrum. That means it's protecting you from both UVB and UVA. And then beyond that, it's really just a matter of personal preference. Find a sunscreen that you both like and that you're comfortable with and therefore will use.

• 19:37Ira Flatow?

  If you have old stuff lying around, is it still good?

• 19:40Speaker 04

  No. So no sunscreen is good past three years.

• 19:43Ira Flatow?

  Ah, I've got old tooths everywhere.

• 19:46Flora Lichtman?

  You've got to get rid of them, Mara.

• 19:47Speaker 04

  And many of them have expiration dates. And so don't use sunscreen past expiration date. There's absolutely no reason to expect that it'll actually work.

• 19:53Flora Lichtman?

  Thank you, Jonathan. Dr. Jonathan Unger is a dermatologist and medical director of the Waldman Melanoma and Skin Cancer Center at Mount Sinai here in New York.

• 20:05Flora Lichtman?

  Today's episode was produced by Kathleen Davis. I'm Flora Lichtman. Thanks for listening.