Understanding Sunscreen Ingredients And Which Ones You Need - podcast episode cover

Understanding Sunscreen Ingredients And Which Ones You Need

Jul 03, 202519 minEp. 1066
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Summary

Summer means sun exposure, but protecting your skin is crucial due to the link between UV radiation and skin cancer. This episode breaks down the science behind sun damage and explores the differences between mineral and chemical sunscreens. A dermatologist answers common questions about SPF, reapplication, sunscreen in makeup, sensitivity, and how sunscreen affects vitamin D production, offering practical advice for choosing and using sun protection effectively.

Episode description

Summer is here, which means it’s the season for soaking up the sun. But it’s important to do so responsibly, considering the strong link between sun exposure and skin cancer. There are a lot of sunscreens on the market, so Hosts Flora Lichtman and Ira Flatow join dermatologist Jonathan Ungar to discuss what ingredients to look for and how they work.

Guest: 
Dr. Jonathan Ungar is a dermatologist and director of the Waldman Melanoma and Skin Cancer Center at Mount Sinai in New York, New York.

Transcripts for each episode are available within 1-3 days at sciencefriday.com.

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Transcript

Understanding Sun Damage & UV Radiation

Hey, I'm Flora Lichtman, and this is Science Friday. Today in the show, sunscreen. What to look for and your burning sunscreen questions. 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. 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. Thank you for having me. 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?

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 subspectrums. 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. Thank you, atmosphere. 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 the damage, excuse me, can ultimately lead to the development of skin cancer.

And which one do we have to be most worried about or both? 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... 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. You know, so I have young kids and it was drilled into me by...

Mineral vs. Chemical Sunscreens Explained

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? 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. That's the mineral. Correct. And then the other ones are what we call chemical 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. 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 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. 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.

But is there any truth to this idea that chemical is less safe for little kids than mineral? I would say the jury is still out. There's 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 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.

Common Sunscreen Questions & Regulations

All right, let's go to the phones. A lot of people want to talk about it. Should we try Liz in Wyoming? Go ahead. Hi, Liz. Hello. Hi there. Hello, this is Liz. Hi there. Go ahead. Hi. My question is about sunscreen in... makeup products there's 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's sort of the truth about makeup or products like that that include an SPS? 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. If the UV index, which, you know, that's a new term I'm introducing here.

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

I am here. Hello. Go ahead. 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. So that's a really 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. playing a very difficult guessing game. 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. 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. Stay with us. 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 make an impact by going to sciencefriday.com slash donate.

Any amount you can give helps to sustain Science Friday programming in this critical moment. Again, that's sciencefriday.com slash donate. And thanks. Support for Science Friday comes from the Alfred P. Sloan Foundation, working to enhance public understanding of science, technology, and economics in the modern world. Have there been any advances in sunscreen, like in the last 20 years?

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 I 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 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. Because no one's doing the studies or? It depends who you ask. I think the FDA would argue that they have to request voluntary submission of data from the company.

that make the sunscreens and they've been a little slower to provide that. 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? 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. Is that SPF 100 then? Probably a billion.

But that's the ultimate, right? Yes, exactly. You don't want to put that all over. So you mentioned that in different countries there are different ingredients. Do you have patients who smuggle in sunscreens who have their favorite overseas brand? baby formula, we see this too. I'll never name names, but the answer is absolutely. I have many patients, for instance, where there's a particular brand of sunscreen that they love that's available in Europe, for instance, even in Canada.

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 a tube or two for your own use, no one's going to say anything. If you have three suitcases filled with it, the... Customs officers might bring an issue because you can have it, I believe, but I don't know if you can sell it. Let's go to the phones. Let's go to Laura in Corvallis. Hey, Laura. Hey.

Sunscreen Use and Vitamin D Production

I'm wondering about vitamin D production when you're using a sunscreen. Do they use it a lot and I'm just concerned I use it year-round? And does it block the vitamin D production? Yeah. 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 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 responding.

for the production of vitamin D. And so this is 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. Like vitamins? 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. 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 your risk of cancer. I'm not going to tell you which one, but you get to choose which one you want to use. Can you walk us through SPF? What is it and how meaningful are the distinctions between...

Decoding SPF and Eye Protection

50 and 70, for example. 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 sun protective factor, and it's a... 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 on the other and start exposing you to uh 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 um so spf

and SPF 50 doesn't tell you one is two-thirds longer than the other. 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 to 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 not regulated, that number by the FDA. It's at least a 50, but it's sort of a question of whether you trust... the manufacturer that it's providing 70 or 90 in their labs. We're talking about sunscreen to protect your skin. What about your eyes? Should we be wearing those UV blocking sunglasses? 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 melanoma, as an example, 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. Let's go to the phones. Let's go to Brooke in Wisconsin. Hi, Brooke. Hi.

Reapplying Sunscreen & Shopping Tips

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 that? 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 it be on there. 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... you know, err on the side of caution. If it's two hours, do it every hour and a half to hour and 45 minutes.

I, 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. This is a very dermatologist thing to do. Yes, exactly. I was going to say, this may be too crazy for me. but otherwise it's easy, just easy to forget. And then of course, you know, if you're getting in the water, this 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...

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 it? Do I have to reapply it at two hours? Do I have to reapply it at 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.

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

If you have old stuff lying around, is it still good? No. So no sunscreen is good past three years. I've got old tubes everywhere. You've got to get rid of Amara. And many of them have expiration dates. And so don't use sunscreen past expiration date. no reason to expect that it'll actually work. 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.

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

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