ZACH: All right. I'm here with Annie Christenson, a medical aesthetician here at Houston Methodist. Thanks for being on the show today, Annie.

ANNIE: Thank you for having me.

ZACH: Sunscreen. A very common household item, something that we all use — or we all should use, certainly. First question for you, Annie. Why do we wear sunscreen?

ANNIE: There's lots of good reasons to wear sunscreen. Our first one is we don't want to get burnt. I mean, that's really why we all have started to wear sunscreen as we were kids being outside. You know, we didn't want to get that sunburn. But as we get older, why do we want to wear it? So, it protects our skin from skin cancer — a big thing that I see a lot of in the office that I work at. We deal a lot with skin cancers, so I know the benefits of wearing that sunscreen since that’s where it can lead. And then the other thing, of course, is anti-aging. Being an aesthetician, I treat skin all the time — and it's because we want our skin to be as healthy and the best looking that it can be. Sunscreen has to be one of the best products that you can use for keeping your skin looking young. So, you know, those are really some good reasons to wear that sunscreen.

ZACH: Yeah, we talk so much about preventative medicine, preventative care. Sunscreen is like an ultimate use of that.

ANNIE: It is. It is. It definitely is. People will say, you know, what's the one thing I need? I’ll say: sunscreen. That's it. There's all these million-dollar products you can use, but if you're not putting sunscreen on your skin, you're really not doing yourself any benefit.

ZACH: In my research, I found that there are actually two kinds of sunscreen: physical sunscreen and chemical sunscreen. This was news to me when I started looking into this. I just thought there was sunscreen. Could you explain to us the difference between those two?

ANNIE: Chemical sunscreen has been around for a long time and is what you're going to find on the shelves most of the time. But, if we go way back to thinking about people surfing, what did they have? Those big white stripes on their faces? That's zinc oxide. That's physical sunscreen. And we've always known that's the best sunscreen. And that's why on the beach, you'll always see those. And then they came out with fun colors and stuff just to make people wear them, because you're going to get a better coverage with it. But they're not very elegant to wear. They're thick, they're heavy. But now they've become more elegant and they're better and easier to use. So physical sunscreens — just to give you an example of what they do — put a coating on your skin. The sun comes down, hits it, bounces off. A chemical sunscreen will actually absorb the sun into it and then turn it into heat and release it. So that's how they actually — and easy way to say — how they work.

ZACH: If you go to the store and you just buy a generic sunscreen, right, is that going to be physical or chemical?

ANNIE: So, you have to look at the label.

ZACH: Okay.

Annie: Yeah, you're going to find both. You're going to find a lot more physicals coming out now just because we found that they are much better on the skin. But you do have to read the label to see. And sometimes you have to turn the box over to find it.

ZACH: Read the fine print, right?

ANNIE: Yes. It's not always on the front.

ZACH: So, for the average person who goes to the beach…I don't know, a few times a year…right? I mean, we're not too far from the beach here in Houston. So, I always enjoy a good weekend down in Galveston, right. if I’m going, I don't know, six times a year I go to the beach, should I use physical or chemical then, at that point?

ANNIE: You can use either one, okay. They're both good. It depends on your skin, for one. If you are more sensitive skin, then a lot of times a physical is going to be better. And if it really is just that you're going to the beach and you're going to be out in that sun all day, then I would say choose a physical. It's going to be better. Chemical is really nice. It can be a little bit more elegant, easier to use sometimes — so that may be more of your everyday [sunscreen], but [the physical sunscreens are] getting better. And I always do say the bottom line with sunscreen is going to be: Which sunscreen do I use? The one that you're going to wear.

ZACH: Yeah, gotcha. Well, to that point about what you're going to wear, I remember being a kid and like, you know, your mom always makes you put your sunscreen on, you’re going to be out all day…that kind of thing. And you’re always like, “Ah, mom!” and it gets in your face and she has to help you...it's something you don't look forward to, but you put it on, right? And then, you know, we got a little older and they came up with spray sunscreen, right? And so I've always wondered, is there a true difference in the ability for that sunscreen to protect you: spray versus like physical lotion, like the classic white stuff you rub on your face and your skin? That versus the spray on?Because the spray on, you know, as a consumer…much more convenient, much less of a taxing procedure to put it on. But is there a tradeoff there for the convenience of the spray?

ANNIE: So, sprays are definitely…we think of them as easier, but you have to realize the way that you're using it. If you read the label on it — and I'm always saying read the label, read the label — because your spray is definitely going to be easier to just spray on all over, but you still have to rub it in. So, if a spray is easier and you like the way it feels — sometimes they can be a little lighter weight on or, you know, sometimes you can spray a child easier with it, or if you're by yourself and you want to get your back it might be easier to spray on — so, a spray can be easier to use. But I have had more people tell me that they have had serious sunburns when they're wearing a spray over a lotion. Why is that? It shouldn't be, because the SPF should be exactly the same. They shouldn't be any different that way. So, we're wondering: Is it because you're not getting it on correctly? Do we need to apply it better?

ZACH: Yeah. I mean, not knowing any of the science at all, that does make sense to me about how you apply it. Because, you know, with the lotion, you really got to rub it in. And all this stuff with the sprays, it's kind of tricky. Like, oh, I just kind of waft it around my skin and it's fine. But, no! You still have to rub it into the skin.

ANNIE: Yes. And you have to apply enough. Because it's easier to apply not enough or, you know, a lesser amount with a spray. So, sometimes you do have to worry about getting everything. And then on your face, you can't really spray it in your eyes and you don't want to be breathing while you're spraying it, so you do have to be very careful. And you don't want to spray it into your hand and then apply it, because it will not penetrate into the skin correctly. It needs to be sprayed right on the skin.

ZACH: Okay. So, interestingly enough, I was on a boat in Florida not too long ago — like a group boat excursion. And they said, “Hey, if you have spray-on sunscreen, spray in your hand and then rub it onto your skin because we don't want it getting everywhere.” And you know what? I got sunburned and now I understand why.

ANNIE: So, that's another thing. You know, the spray-ons are not the best. They can make you [accidentally spray] on other people or other people are getting it in the way. It can be slippery if it gets on the floor...But I do like the spray for reapplying — so it might be nice in your bag later on in the day.

ZACH: About how often should you reapply sunscreen? Because — I think people are going to start their day, they know they're going to be outside all day — oh, let me put my sunscreen on, but once you get out there, it kind of leaves your mind. You just go about your business the rest of the day. Next thing you know, you might be sunburned. So, about how often or what kind of frequency should you reapply sunscreen?

ANNIE: So, sunscreen should be applied every 2 hours.

ZACH: 2 hours! Wow.

ANNIE: That's what the label says. But. Here's where that changes. If you're going to be inside in your office all day, you don't need to reapply it every 2 hours. If you're going to be on the beach or you're going to be out riding your bike or walking and you're going to in the sun or in and out of water for several hours, then absolutely you want to reapply every 2 hours. Because sunscreen is not towel-proof. It's not sweat proof. It’s not rub-proof. So, you have to reapply it.

ZACH: I've seen some that say like waterproof. What does that mean exactly?

ANNIE: So, a lot of them are [water resistant], and most of them it's up to like 80 minutes is what you'll find. What that means is you can get it wet and it's going to stay on. If it doesn't say that, then if you're going to go swimming, it can wipe right off — because we do know [it’s] completely water soluble, so it'll just come right off and then you are exposed. So, if you know you're going to be in the water, you do want to find something that is water resistant for those 80 minutes at least. But any time you go in the water — doesn’t matter if you just put it on, you go in the water and you’ve only been in 15 minutes and you come out and you towel dry — you need to reapply because you just wiped it off.

ZACH: Okay, 2 hours. Wow. I can't even remember the frequency that I've reapplied, but it's definitely been more than 2 hours.

ANNIE: Yeah, easily done.

ZACH: Now, you mentioned sitting in your office and that sort of thing. Do you recommend you wear sunscreen beyond just like a day outside, a day of the beach, a day playing soccer? Like, are you recommending you wear sunscreen on a more regular basis than even that?

ANNIE: Yes, every day. Sunscreen should be applied every day, every morning. And you'll find that they are becoming much more user friendly to put them on every day — meaning that they're comfortable. Like you were saying when you were a kid, you didn't like how it felt. Now they feel good. It can be part of your moisturizer, your sunscreen altogether. But you get UVA rays and, well, all sorts of rays — UVA, UVB, we get rays from our computers, we get rays from these overhead lights. Yes, you need to be protected all day long, no matter what.

[Music plays to signal a brief interjection in the interview]

KATIE: Annie mentioned both UVA and UVB rays. UV rays, or ultraviolet rays, are one of the many different types of rays that are present in sunlight, and the most damaging to our skin. So, what's the difference between them? UVA rays penetrate more deeply into the skin and can contribute to the formation of skin cancer, as well as premature skin aging changes such as photo aging — a.k.a. wrinkles. Sunlight contains about 500 times more UVA rays than UVB rays. And UVB rays are the ones responsible for producing sunburn. They also play the greatest role in causing skin cancers, including malignant melanoma. In the United States, the National Weather Service assigns almost 60 cities with a UV index number. This is a number that rates the strength of ultraviolet rays from a scale of 0 to 15. 0 to 2 is minimal, with an average of 60 minutes of sun exposure until sunburn and a recommendation of sunscreen and UV sunglasses. 10 to 15 is very high, with an average of 10 minutes of sun exposure until sunburn and a recommendation of sunscreen, UV sunglasses, as well as hat, umbrella and even the avoidance of the midday sun. All the numbers in between — 3-9 — also have their own recommendations. We encourage you to check those out on the National Weather Service's website.

[Music ends, sound effect signals commercial break, commercial plays and sound effect signals return to the interview]

ZACH: I have gotten sunburned — or, maybe not burned but at least a little red — from just even driving in the car in the summer. Got shorts on, then thinking like, oh, why are the top of my knees red? Oh, the sun has been coming through these windows.

ANNIE: And, yeah, here in Houston, the sun is out a lot and it takes a long time to get anywhere when you're commuting. So, you can be sitting in the car for 30 minutes or longer, and you definitely can get sun in that time. Take my commute, for instance. I'm in the car for maybe an hour to an hour and a half sometimes. I drive straight east to get here, straight west to go home. So, I'm right in the sun each time.

ZACH: To that point, if you know you're going to be outside, but you know that it's a cloudy day or you're going to be in the shade, you should still apply sunscreen?

ANNIE: Very good question, because — “Yeah, it's cloudy. I don't need sunscreen.” Yes, you do. Those rays penetrate straight through those clouds. You'll probably think of it — and a lot of people will say — I got my worst burn when it was cloudy out. And that's why, because you don't feel that heat. So, the UVB comes through, which is the burning ray. Now, if you're under a tree and you've got shade, that's physical coverage. So that can help. You have to remember, reflections, too, though — cement can reflect the heat and sun, and water does as well.

ZACH: Let's talk about SPF. First of all, what is SPF and then how do we know what number is best for us?

ANNIE: SPF is the sun protection factor, and that has been around for a long time. And it is FDA-regulated. So, what you'll find is...I believe that anything over 30 is what you should have on. And that's really going to give you like a full day protection. The way that the FDA actually regulates it is: If it takes 15 minutes for you to burn, then times that by the [SPF] number. So, you take your 15 minutes times, you know, SPF 30 and what does that give you? Like seven, eights hours. So that's going to be how long you should be able to stay out. Now, I don't think it’s always enough, so you should always [have a] minimal of 30 if it's a regular day when you're just kind of running around, not really worrying about being out in the sun or the beach or that kind of thing. You can find higher ones now, and that just means they're going to give you longer protection — not necessarily more protection, just longer in the day protection.

ZACH: Wow. Okay. I had assumed that it's like, oh, I'm going to get a 50 and be double protected. Because I'm more of a fair skin myself, I always default to like around the 50 SPF.

ANNIE: Which is why you can go a little longer before you reapply when you maybe are thinking, oh, every 2 hours. But I can go three and I'm still okay, okay — because you're in [SPF] 50, not 30.

[Music plays to signal a brief interjection in the interview]

KATIE: Some moisturizers contain SPF, so you may be wondering if yours can double as sunscreen. It depends. Annie mentioned that a daily sunscreen should have an SPF of at least 30, preferably more than that. And a lot of moisturizers out there have less — some are as low as SPF 15. This isn't enough. You'll need to check the label of your moisturizer to be sure it meets your SPF needs.

[Music ends to signal return to the interview]

ZACH: So, we have a lot of sunscreen in our house — we leave it in back of the cabinet somewhere. And it's like, "Hey, the pool opened. Where's the sunscreen?” You pull it out of the back of the closet, right? You don't think about it, you put it on. But is there an expiration date for sunscreens? Is that something we should be looking out for before we, you know, think we're being protected and maybe we're not because our sunscreen is three years old.

ANNIE: Exactly. Sunscreen does have an expiration date on it. And it's very important you look for it. So, it's usually crimped in it, like in the top of the tube, or printed on there somewhere. It's always going to be on the box generally as well. And it's very important to look at it. Sunscreens usually will expire in about a year. Does that mean it's going bad or just quits working immediately? No, [but] it loses its efficacy after that year — so you do need a new one.

ZACH: Okay.

ANNIE: I always tell people new sunscreen every year. Don't baby your sunscreen. Use it up.

ZACH: Yeah, I mean, I probably get criticized for putting too much on, lathering up too much. First of all, I don't want to get a sunburn.

ANNIE: Yes.

ZACH: And what is it for? It’s there to protect you! So, I'm all about putting as much on as possible. I've had some pretty bad burns in my time, and I just don't want that to happen again if I can avoid it. So, I probably put too much on, but that makes me feel better not knowing it's going to expire in a year anyway.

ANNIE: Exactly. And there is not a “too much” — you can't overuse your sunscreen.

ZACH: Gotcha. But, in the unfortunate cases where you forgot to put something on, or you didn't put on enough on or didn't reapply and you do get sunburned…the best remedies for that? Aloe vera is always something that I have been taught. Is that still the number one remedy?

ANNIE: You always hear aloe vera, yes. And ouch! Nobody wants that sunburn. But, sure, it happens. Yes, a little aloe vera, you can use a cool compress. Depending on how bad it is, there are sunscreen relief sprays that you can find, because you're not going to want to rub that skin. But if you do get a blister or worse than that, and it's in a large area, you may want to go see somebody about it — but, for the most part, just keeping it cool and little aloe vera should be fine.

ZACH: What kind of procedure would you recommend if you're going to be on the beach for a few days and then like day two you get sunburned. You know you’re still going to be out and about in the sun for a couple more days…do you put aloe vera on and then sunscreen? Or what do you recommend in that situation? Because I'm sure it happens to people.

ANNIE: You really shouldn't go back out in the sun if you have a sunburn. But maybe you want to head to the store and get some sunscreen clothing, which is my favorite thing to do.

ZACH: What is sunscreen clothing?

ANNIE: You know, like the rash guards that people wear — like surfers and stuff like that. So, that's what it looks like. It's basically a swimsuit fabric, but it has a sunscreen in it, generally SPF 50. Especially for people that have light skin, little kids that are going to be out in the pool all day long — that's really what I recommend. Do you still want to use sunscreen? Yes, but I always wear long sleeves when I'm at the pool.

ZACH: Yeah. Well, Annie, thanks again for all your great advice. I'm definitely going to take some of it to heart. Sunscreen is something that, in my life, I put on if I'm going to the beach or if I'm going to be outside playing sports all day or something like that — never really occurred to me that it's something we should be doing daily. Of all the takeaways of our conversation, that's definitely the one I'm going to hold on to the strongest.

ANNIE: Perfect. Yes, that is the best takeaway anybody should have from this. Wear your sunscreen every day. I want to get that out there.

ZACH: All right. Thanks again.

ANNIE: Yes, you're so welcome. Thank you for having me.

[Sound effect signals the end of the interview]