Dermatologist Leon Clark Jr., MD, presents the latest evidence on which methods – from sunscreens to behavioral changes – protect skin from damage, and he sheds light on the preferences of different populations. Here’s help with answering questions on SPF, out-of-favor ingredients, vitamin D synthesis and other concerns, and what to emphasize when advising patients (surprise: it’s not sunscreen).
I'm dr clark uh dermatologist no, maybe a skin cancer awareness month. And I think this topic is um keeping with that tradition of uh kind of continue to educate the public and each other about skin cancer in some protection Now that broader kind of uh scope, some protection is actually pretty dense. So we'll go slowly through some of the photo biology and then we'll kind of continue into some of the recommendations and best practices for some protection. Yeah. Mhm. We'll start with the question here. So a patient with the family history of melanoma and one basil cell carcinoma, which sunscreen should I use this? Uh This is a question that comes up in clinic every day. Uh a is use sunscreen SPF 30 beware hat in particular clothing. C avoid midday sun. D stay in the shade or eat all the above. Okay, sure. You guessed it All of the above. And we'll go over kind of why these things are by layering and some data and some evidence as well. So let's start off with the electromagnetic spectrum and And really most of the light that we see is visible light about 42% of um the electromagnetic spectrum we are is within the visible light spectrum. However what will focus on today is the ultraviolet spectrum. Specifically UV vis a Vis a UBC Is absorbed by the also layer and 0% gets to the Earth. Yeah. Yeah. Go back. Okay so the main effects of UV radiation on normal appearing skin can be both acute and chronic now exposure of the sin of the skin to UV light leads to both acute short term effects I. E. Sun burning and Danny and also chronic longer term effects like photo question of genesis and photo aging all of which are wavelength dependent. All organisms have evolved mechanisms for protecting itself against UV induced killing um And the genome damaging properties of UV light for humans and these including DNA repair processes. Um For the mutations of see the T. And C. C. T. T. Immune mediated removal of damaged cells and antioxidant to defense systems. So we'll both go over the acute and chronic ways in which sun explode with can cause harm your skin. So as we previously discussed um its wavelength dependence. So the longer the wavelength, the deeper the depth of penetration. So as you can see UV. B. And right around the 300 Nanami the spectrum gets right down to the basal layer of the epidermis. That's where melanocytes live. The basal layers where basis of carcinomas derived from and U. V. A. The longer wavelength of light penetrates down into the dermis. And that's really why you're kind of seeing some of the breakdown of the college and some of the photo asian related to U. V. A. And since it does reach some of the deeper portions, only a very small portion of UTA is actually absorbed in the epidermis. So new Tv is really the major factor when it comes to attaining. Especially relating. Yeah. Yeah. So don't be this guy, you know apply enough sunscreen use it regularly. He might have won the race but did not win the award this time. Yeah. So when we get into some protection a little bit more it's more than just on screen. So there have been studies done trying to quantify what americans typically use for sunscreen. And in this part you can see that shade along sleeves are predominantly the molds in which most groups use. And whites have a higher tendency to use sunscreen than Hispanics and blacks. I hear this a lot from an african american patients. I don't need to wear sunscreen. I have zero risk of skin cancer, my melon and protect me. And in those cases I think it's really important to really justify some of their responses. Um and kind of some of their questions about this because really there's been a lot of requestioning this notion that sunscreen will prevent skin cancer, specifically melanoma, especially in the black population. So what I try to frame the sunscreen conversation um with my asking your patience as we're using it in terms of pigmentation, we're using it to prevent photo aging. And you might have a small um increase effective preventing skin cancer from there. So what about some protection and Sundberg and what modes of photo protection are most effective um to prevent some birds? Um in this table there's a Multivariate model that's adjusted for age 10 b. m. i. And education. that compares um the number of sunburns for patients who had shaved long sleeve sunscreen or had and um perlis analysis on shade was the most protective factor as sunscreen in the least protective factor. And I think I have some speculation about why that is but um I will get to that later on and some protection also differs by ethnicity. This is another um survey in which they add what type of some protection different patients use. So chinese predominantly speaking patients in the survey U. Shaped predominantly did not use sunscreen and it was almost the inverse. And the other group. Mm. So we'll pause there in terms of primary prevention. This is kind of an infographic that I give all of my patients when I'm giving them recommendations for how to use. Photo protection number 123 and four before we even get into the sunscreen conversation is really about avoidance and physical protection. So maintaining shades staying out of the sun during peak daylight hours, um wearing clothing that's protective has a ups in it or just fabric that's covering all sun exposed sites, broad brim and sunglasses. And then the last thing I mentioned is wearing a sunscreen as that additional layer of protection. Okay so now we'll kind of get into the meat of our discussion here um And I get this question every hour. Um What SPS should I use? The labels are confusing. I'm not sure about sunscreen I should be using. So a use SPF. 15 since this blocks 93% of you beaver ace, which is enough. B. 30 c 60 or D. SPF doesn't matter. And two answers either B or C. Is great and it depends on the patient population. Okay, I'm sure you all have seen this infographic. This is a study that shows the UV protection level I. S. P. F. And anything over 30. You're really not getting much incremental gain. Um Afterwards. So SPF 30 96.7% of U. V. Blockage. Um and then once you get up to 50 it's 98%. I also know the initial sunscreens were formulated primarily to prevent sunburn. Um So this SPF level is actually only measuring the ability to block UV. B. It has nothing to do with you. Be a that's uh a separate method of testing. So I'll pause here at this chart. I think this is um both confusing and it kind of highlights the number of different sunscreens that can drive patients crazy when they're going um to the store and trying to pick out a sunscreen. So I kind of break this down into kind of the highlights. So currently most sunscreens in the United States combined two or more agents to achieve this broad spectrum status. Um And as scientific I live drew documented the deleterious effects of longer away from U. B. A. Um manufacturers started to develop higher levels of protection against burning agents with longer wavelengths like pencils. Unknowns were combined with UV B. So that there are more efficacious. The insoluble products down at the bottom of the screen, titanium dioxide and zinc oxide are the two that I actually generally recommended for patients who have some type of sunscreen sensitivity. Or they say they experience burning in sunscreen. Those are physical protections whereas ones at the top of chemical protective, so different mechanism of action. We'll kind of talk about some of the chemical sunscreens and systemic absorption and on some of the data and issues surrounding those that are helping us. Mhm. Mhm. Mhm. Mhm. So we'll break down some of the sunscreen realities. So the SPF written on the bottle is what's achieved during test conditions. Now, during these test conditions, what they do is they put two ounces um of the sunscreen and they assume that the human consumer is going to use that same amount when they're applying it every time. Um This is not the case, we apply about a quarter as much as we're supposed to be using. And thus the truth SPF that we're getting from the sunscreen is much less. So again, um they're using two mg per centimeter square and most people are only using about 20.5 mg per centimeter squared. So we've shown through studies that when doing so you're really if you're using SPF 30 sunblock And you're only putting .5 mg per centimeter square And you're really only achieving about three SPF. Yeah. And of no melon in and in and of itself is almost the equivalent of about four SPF. So you're really kind of back to baseline if you are a darkly pigmented person. Yeah. Uh Mhm resume sharing. How is that? Okay, I'll keep going. Alright so ultraviolet radiation is a continuous spectrum whose effects change as wavelengths um increase in decrease and the amount of U. V. R. That reaches to your varies each day according to the season and geography and the location that you are so UV UV a rays are lower in energy than New VB. There are 20 times more abundant and they're relatively unaffected by altitude or time of the day or atmospheric conditions. So you've a is also present throughout the year, all times of the day. It's unaffected by seasons. So you know this is just kind of showing you that even though we have this broad spectrum there are different wavelengths of life penetrate at different times of the day and they of course exert their effects at different parts of the um cutaneous anatomy depending on the wavelength. Yeah. Look so again, as we discussed before, SPF only applied to U V. B. U V A. UV radiation is lowered, energy is more abundant. It's present all the time. Um And it contributes because it penetrates down into the darkness. Um It contributes to aging, contributes to skin cancer. Um immuno suppression and most of the photo derma titties, photo toxic eruptions. Photo allergic eruptions. Are you the a mediator you via driven. Mhm. And no note there. That's important because in terms of recommending sunscreens and photo protection for patients who you suspect is having a photo dermatitis. Yeah. let's talk about some of the labelling changes for the sunscreens that mm Had gone on really within the last decade or so and more and more is coming of this in the next year. So all sunscreen shift after 2012 um had to have a standardized labeling. So anything that's labeled as broad spectrum, they have to prove that they can both absorb UVA and UVB proportionately to the same amount. Um And some screens that um Have an SPF number will have an SPF number and anything a greater than 30 is what the 80 recommends And water resistant and sports sunscreens is something that I think a lot of patients have questions about. So I'll break that down a little bit in my next slide. But basically water resistant means water submersion for 14 minutes and the sunscreen is still has an effect And then 80 minutes is similar as well. Yeah, so let's go to this question. A cyclist patient comes to your office, she complains that she cannot tolerate any sunscreen. They all burn or itch when she applies them. What do you do? Okay speaking. Mhm. Try a stick or vastly and based on blocks and you know, this is something that we hear a lot about. Um I apply the sunscreen doctor and my face starts to burn. Yeah, I think I'm allergic in truth. Most people who complain of stinging from sunscreens might not have a true reality. True allergy. It could be an irritant dermatitis secondary to an underlying process that makes them more susceptible to an irritant like rosetta or sensitive skin, thicker sunscreens like Vaseline based or stick some blocks um are sold and sold in surfing shops and they're usually less irritating. So when patients say um they have some irritation. Sometimes I'll actually recommend try a surf shop, check it out, see if there's any sunscreens there um that you might like. And lastly some blocks that are physical protectant like zinc and titanium um tend to be less irritating. Yes. So again about a note about sunscreen allergy, It's rare but it does exist. Um The offending substance can be very depending on which sunscreen it is, it can be a fragrance, it can be a preservative, it can be the sunscreen agent in and of itself, like a Provenzano oxygen zone. So for a true sunscreen allergy I typically just go right to Vani Cream SPF 60. Um That is hypo allergenic and doesn't have any contributing common allergies in it. Okay so next question, when do I reapply? It says water proof. Do I need to reapply? How often what if I'm sweating now? These are questions that come up as well so ain't no need to reapply and then B. Through D. Are between one and six hours. Uh huh. 72 hours. So a note about clothing and sunscreen. So what I typically tell patients to do is make sure you apply your sunscreen at least 15 minutes before you go outside to allow it to absorb and penetrate. So what it's actually doing his job, Wait about four minutes before applying your t shirt over your sunscreen to reduce the SPF you achieve and waiting eight minutes actually results in only 25% reduction. So if you sneer on your sunscreen everywhere and then immediately apply your clothes, data suggests that you're just kind of taking off the SPF effect. Some more controversies um sunscreen allows us to stay in some longer so I can stay outside longer. That's not true. The incident to skin cancer has actually increased since sunscreens have become more available. And you know, some of the controversies regarding whether sunscreens are carcinogenic or hormone disrupting what the environmental impact is, especially in regard to coral reefs and sunscreen and vitamin D deficiency. What if I have more melon isn't, I can't absorb vitamin D. As well, shouldn't I not wear sunscreen and we'll go through these. Um So some protection by beach umbrella versus high SPF sunscreen. This notion that L. A. Fine um gonna wear sunscreen, I can stay out longer. And this is actually a study that's been done um from lake Lewisville texas from um with Fitzpatrick 123 These are people who will eventually burn if they stay out in the sun long enough. And they were assigned to two groups. One group was just beach umbrella and one group of sunscreen with SPF 100. They were told to stay on the beach for 3.5 hours and were evaluated 24 hours later for a sunburn. Now, interestingly, 78% of the participants from the umbrella group developed a sunburn, whereas 25% um they're using sunscreen. So just the umbrella alone cannot prevents you from getting a sunburn. Yeah, So here's a list of some of the sunscreen ingredients that have been kind of on the press at some point hot on the press because of some either allergic reactions or um some adverse effects that have not yet been quantified. So we'll go through each of them. The first ones, Abba, this is an old school um sunscreen product that's no longer use an active markets. It's one of the most common contact allergies. It's also been shown to increase Christina genesis. So most products are labeled palette free because it's no longer allowed in the United States. Okay. Yeah. Retinal talented is a derivative of vitamin A. So similar to Trenton on an apple lean to zero team. These vitamin A derivatives have some some anti aging and antioxidant effects. Um In mouse models did slightly increase the risk of skin cancer. So um generally when when patients are saying that they use a vitamin A derivative in addition to their sunscreen, I typically tell them to just go with the sun protective factor and then apply a vitamin A cream afterwards. Mm. Mhm. Beautiful Hawaii. I'm showing this picture because of the sunscreen coral reefs controversy that's still kind of hot Um hot out there. So in January 2021 Hawaii banned the sale and distribution of sunscreens containing oxygen zone like Tennessee. Um And lab data did show the oxygen zone may be activated by some white to form free radicals which also damages D. N. A. Um And the CDC study the entire levels of internal oxy Ben's own with lower birth weights. And that data has not um has not been substantiated as of yet. And there is an allergic contact dermatitis potential oxy Ben's own. The Benzos unknowns are the group of chemical sunscreens that you're most likely to be allergic to. Um Lastly in terms of its environmental impact, um Oxy benzos not sufficiently removed by wastewater treatment plants. So it has a potential to accumulate coral reefs leading to the bleaching and the deaths of the reef. And that's which led to this kind of movement for Hawaii to ban sunscreens with. See that is on it Now. Tennessee was similar in that in 2021 Hawaii banned the sale and distribution of the sunscreen for similar reasons, not sufficiently removed by wastewater. And in rat studies showed um anti androgenic vaccinate, anti thyroid effects. So this is a picture that's come up in the media a lot regarding the sunscreens and the chemicals and the safety for the animals and dolphins in the reefs. And one thing that I do tell patients is that even though these two products um oxygen's um they were studied to found to accumulate in these waters, we don't know the scope of the problem. So when I tell them that if you're worried about the coral reefs and you're trying to choose a sunscreen, just go for the physical blockers, something with zinc or titanium dioxide in it. Yeah, so some protection and vitamin D. Again kind of re emphasizing this point um that people who use sunscreen alone still have an increased risk of vitamin D. Deficiency. So it's not the sunscreen in and of itself. Um that's causing your vitamin D. Deficiency. So when people say I need to get lots of sun in order to get enough vitamin D. Um What I typically tell people is, you know, if you do not have a restricted diet, if you're kind of an adult eating kind of a regular diet in the United States, then more than likely you're able to get enough vitamin D. From your meals. So it's simply synthesized through the skin but it's really obtained through the diet and there's no evidence that getting vitamin D. From the sun is better than the diet. Yeah. Okay. And there may be some discussion regarding its anti inflammatory effects, autoimmune effects and its effects regarding cancer. But those results are clear yet. Yeah, so again, my advice to patients at this point is 123 avoid the sun, stay in the shade, avoid midday sun if you have to go out wear protective clothing first. And then we get into the discussion of wearing sunscreens. I typically go um physical protection first over chemical sunscreens if they're going to go out to the beach, otherwise if they're cycling or exercising something that's water resistant as well. And then lastly, the vitamin D. Issue only for those who are at high risk of efficiency. Right? Yeah. So I'll pause here and just say um kind of an interesting statistic that I saw the other day. There's not enough dermatologist to see all skin cancer patients if everyone wanted routines can examine. So there are 10,000 dermatologists. Each one have to see over 10,000 patients per year to do a full body skin exam for every adult in the United States. So it's really kind of up to our collective group to not only do the Sun protection education, but also start doing some skin exams and also just empowering the patients to do their self exams and refer but needed mm.