Understanding Sunscreen Ingredients And Which Ones You Need

IRA FLATOW: This is Science Friday. I’m Ira Flatow.

FLORA LICHTMAN: And I’m Flora Lichtman. Are you ready to soak up the sun? Today marks the first day of summer. And that means a few of my favorite things– barbecues, beaches, broiling under the sun, which also means it is 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? And what do you want to know before you lather up? If you have burning sunscreen questions, give us a call– 877-4SCIFRI, 877-4SCIFRI.

Here to shine some light on some of those questions is Dr. Jonathan Ungar, a dermatologist and medical director of the Waldman Melanoma and Skin Cancer Center at Mount Sinai here in New York. Welcome to Science Friday.

JONATHAN UNGER: Thank you for having me.

FLORA LICHTMAN: So let’s break down first– 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?

JONATHAN UNGER: So a tremendous amount of electromagnetic radiation travels from the sun down to our skin. There are many aspects of this 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 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.

FLORA LICHTMAN: Thank you, atmosphere.

JONATHAN UNGER: 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.

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

JONATHAN UNGER: 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.

FLORA LICHTMAN: 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?

JONATHAN UNGER: 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 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.

FLORA LICHTMAN: That’s the mineral?

JONATHAN UNGER: 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.

FLORA LICHTMAN: [LAUGHING]

JONATHAN UNGER: So the mineral sunscreens work differently, though, which explains, in fact, why some people don’t like to use them, because they have this whitish cast. The way that they work, physical blockers, is by blocking and reflecting light. 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.

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

JONATHAN UNGER: 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’s– you feel comfortable with. I would say it’s– 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– excuse me, 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 are 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.

IRA FLATOW: All right. Let’s go to the phones. A lot of people want to talk about it. Hi. Deborah in Pittsburgh, welcome to Science Friday. I’m having a little trouble getting– Deborah, are you there?

FLORA LICHTMAN: Should we try Liz in Wyoming?

IRA FLATOW: Go ahead. That’s true. Hi, Liz.

AUDIENCE: Hello.

IRA FLATOW: Hi, there.

AUDIENCE: Hello. This is Liz.

IRA FLATOW: Hi, there. Go ahead.

AUDIENCE: Hi. My question is about sunscreen in makeup products. There is a ton of products out there that claim they have SPF and, 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? Do you have to reapply them? And what’s the truth about makeup or products like that that include an SPF?

JONATHAN UNGER: 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. 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– that 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 I’m a– 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 OK. 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.

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

AUDIENCE: I am here. Hello.

IRA FLATOW: Sorry about that. Go ahead.

AUDIENCE: No problem. Hi. 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.

JONATHAN UNGER: So that’s a really great point. 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 a– your dermatologist, or find one. And then they can help you to isolate those products. Otherwise, you’re playing a very difficult guessing game.

IRA FLATOW: Thank you.

FLORA LICHTMAN: Have there been any advances in sunscreen in the last 20 years?

JONATHAN UNGER: 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 changed a bit. But really, 1999 is when the last real set of guidance and rules so far as it 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 there– 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.

FLORA LICHTMAN: Because no one’s doing the studies, or–

JONATHAN UNGER: 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. They’ve been a little slower to provide that.

IRA FLATOW: What is the difference– when I go to the beach and I see the lifeguards, but they have this white nose, and– are they putting on something different than I’m doing as a sunscreen?

JONATHAN UNGER: 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.

FLORA LICHTMAN: Is that SPF 100 then?

JONATHAN UNGER: Probably a billion, I would say.

IRA FLATOW: But that’s the ultimate, right?

JONATHAN UNGER: Yes, exactly.

IRA FLATOW: Yeah, you don’t want to put that all over.

FLORA LICHTMAN: 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, like baby formula– we see this, too.

JONATHAN UNGER: I’ll never name names. But the answer is absolutely. I have many patients, for instance, 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 you have three suitcases filled with it, the customs officers might have a– might bring an issue because you can have it, I believe. But I don’t know if you can sell it.

FLORA LICHTMAN: Let’s go to the phones. Let’s go to Laura in Corvallis. Hey, Laura.

AUDIENCE: Hi. I’m wondering about vitamin D production when you’re using a sunscreen because I use it a lot. And I– just concern of– I use it year-round.

FLORA LICHTMAN: And does it block the vitamin D production?

JONATHAN UNGER: 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 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 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–

FLORA LICHTMAN: Like vitamins?

JONATHAN UNGER: –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.

FLORA LICHTMAN: Can you walk us through SPF? What is it? And how meaningful are the distinctions between 50 and 70, for example?

JONATHAN UNGER: 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 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 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. So SPF 30 and SPF 50 doesn’t tell you one is 2/3 longer the other. SPF 30 blocks about 96.8%– so let’s say 97%– of UVB when used properly. And that’s really important. You can put a tiny, little drop for your whole body or you can put a huge amount. This goes to the question of what you’re putting on your nose when it looks so white. SPF 50 blocks 98%. SPF 100 blocks around 99%.

It’s interesting. And just to complicate an 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 a question of whether you trust the manufacturer that it’s providing 70 or 90 in their labs.

IRA FLATOW: We’re talking about sunscreen to protect your skin. What about your eyes? Should we be wearing those UV-blocking sunglasses?

JONATHAN UNGER: 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 it as well.

So the answer is yes. We really all do need to be protecting– the eyes, like our skin, are remarkable tissues that have the– a 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.

FLORA LICHTMAN: Let’s go to the phones. Let’s go to Brooke in Wisconsin. Hi, Brooke.

AUDIENCE: 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 that.

JONATHAN UNGER: 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 2 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 2 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 do that throughout the day.

FLORA LICHTMAN: This is a very dermatologist thing to do.

JONATHAN UNGER: Yes, exactly. I was going to say, this might be too crazy for most. But otherwise, it’s easy– just easy to forget. And then, of course, 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 minute or water-resistant up to 80 minutes.

But that’s hard for people to even know, what am I doing? I was in the water for 35 minutes. So does that mean I don’t have to reapply it? Do I have to reply it at 2 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.

FLORA LICHTMAN: In the 30 seconds we have left, tips for shopping– what should I look for? What should I avoid?

JONATHAN UNGER: 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.

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

JONATHAN UNGER: No. So no sunscreen is good past three years.

IRA FLATOW: Oh, I’ve got old tubes everywhere.

FLORA LICHTMAN: You got to get rid of them, Ira.

JONATHAN UNGER: 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.

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

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