Thanks to Curiosity Stream for
supporting PBS Digital Studios. It looks like I’m wearing
really bad tanning oil. Hey, I’m Dianna. You’re watching Physics Girl. Just relaxing here in the shade
on this beautiful summer day. Isn’t that right, Derek? Yeah, that’s right. OK, but you’re not
even in this video yet, so you just chill. So a couple of months ago, a
few guys got in touch with me and told me that they had
access to a UV camera. Do you know what that is? Yes. Basically, it’s a
camera that allows you to see the world
in ultraviolet, which meant a few things for me. It meant that I could see
what this looks like in UV. I could see what your face
looks like without any lotion or makeup on in UV. And I could see how
sunscreen shows up on your face in ultraviolet. And so I said, yes, please
do come visit me in San Diego and bring your UV camera. And so the guys from the very
well-made YouTube channel, How to Make Everything,
showed up at my house. And this is what we did. Yeah, on your pants. Your pants are so
tigress right now. You’re going to have some
weird tan lines after this. I was just thinking that. This is so crazy. Oh, they’re devil horns. The bigger the
better, if you ask me. I gotta see this. Is that showing up? Oh, yeah. Oh, yeah. Nice. Yeah, that was the fun day. But I should
explain why I’m here with Derek from Veritasium,
who is also making a video about the world in UV. I’ve been making this
video for like a year. And I’m here to
make him finish it. But for this video, we’re
going to cut in a few times to discuss the
sunscreen controversies. There are a lot
of misconceptions about sunscreens. And we’re going
to clear them up. Yeah. But for now, I’m
going to turn it over to Dianna in the studio. Back to you, Diana. The first thing I
wanted to look into was whether different
SPFs, that is, sun protection
factor, which actually is supposed to indicate how
strong the sunscreen is. But anyways, I wanted to
see whether different SPFs of sunscreen look
different under UV light. And then I wanted to compare
whether high SPFs, like SPF 100, are more
effective than just regular high SPFs, like SPF 50. Here was my thinking. With a UV camera,
things that look lighter are emitting or reflecting UV
light, like the wall behind us. And things that look
darker, like the shirt that I’m wearing, are
absorbing UV light. Which is something
that I think you’d want to know when it comes to
sunscreen, because UV light, ultraviolet light,
of course, is part of the spectrum of light
or electromagnetic waves from the sun. And UV is just on the
far side of the violet part of the visible
light, rainbow, which means it’s a wave that has
a shorter wavelength, which means it has a higher frequency
than any visible light. And in the end, it can do more
damage to molecules like DNA or to cells. And as we all know, it’s
been linked to skin cancer. So my thinking was
that, if you look at your skin with
sunscreen on, you should see that UV light is absorbed. So it should look darker. And yeah, like, when we
put the sunscreen on, it looked like face paint. We were even able to graffiti
the side of the truck with sunscreen. But of course, you can only
see it with the UV camera. So my hypothesis was that the
sunscreen with the highest SPF should look darker
with the UV camera. And so we tested a bunch
of different sunscreens with different SPFs on
a grid on my arm drawn with permanent marker. Here’s what we saw. You can’t see anything. That looks just
like a sharpie. It looks like paint. Looks like metallic black paint. Initially, we saw that
yeah, the low SPF areas do look less dark. You can tell they don’t
seem to be absorbing as much ultraviolet light. But interestingly, there’s
not a ton of difference between the 30 to 110 SPFs. And I’ve heard this
rumor that SPFs above 50, anything really high,
doesn’t actually do anything more than SPF 50. So I looked into the
scientific literature on this. And I actually
found a study that came out just this
year in May 2018 that tested 199 people with SPF
50 and SPF 100 sunscreens. Over the course of about
six hours of sun exposure, the subjects got more
sunburnt with the SPF 50. But they do put a
nice little disclaimer at the bottom of the paper
that leads you to conclude that more research needs
to be done on whether there are more benefits over
the long term of using SPF 100 versus 50. Hey, guys. I just want to pause
on this for a second. Because I still think it’s weird
that I had this conception that above SPF 50, you don’t
get any more benefits. And Derek, let me know
what you think about this. But I– I think I’ve
figured out where that conception came from. And I think that it’s
from a 2011 proposed rule from the FDA, the American
Federal Drug Administration– they proposed a rule that
would limit the maximum allowed SPF labeling to 50 plus. Thoughts? I also don’t
think it’s strange the conception that the high
number sunscreens are all basically equivalent. When I lived in
Australia, people were limited to putting only 30
plus on the sunscreen bottles. And now, they’ve moved
that up to 50 plus. But it’s still, I
think, a good idea. Because as those
numbers increase, you’re getting
diminishing returns. So what’s the difference
between 50 and 100? Well, it’s not really that much. Because a lot of
how effective they are comes down to
how much you apply and how well you apply it. So I think it’s just
a marketing gimmick to say that this is a 75, or
this is an 80, or this is a 90. So obviously, SPF and the
efficacy of different sun protection factors is still
an active area of research. Anyways, back to
the fun day at hand. When we were looking
at the sunscreens with the different SPFs, we
tried a different sunscreen with SPF 25 and
something weird happened. It was actually lighter. Like, really light. This means that it’s
not absorbing UV light. But could it still
be sunscreening? Yes. If it reflects UV light,
which is most likely what’s happening here with
this sunscreen that has zinc oxide in it,
which is a substance that’s known to reflect
some types of UV light. So, this is where I
got really confused. I started looking up some
sunscreen ingredients and what they do and
why some are reflective and others are absorptive. And I ended up going
down the rabbit hole of sunscreen controversies. I’ll get to the
discussion on health effects of different sunscreen
ingredients in a minute. But I did find that Hawaii
recently banned some sunscreens from the state. The reason why is
that ingredients oxybenzone and octinoxate
were found to be contributing to coral reef bleaching,
a process whereby coral polyps expel the little
algae living inside of them– actually sounds
like an exorcism, but it is, in fact, a bad thing. So starting in 2021, Hawaii
is banning any sunscreens with those ingredients. This ban was based off
of recent research. Which begs the question,
are the health effects and environmental effects
of sunscreen ingredients not well known? OK, I’m just going
to pause here again. Because I feel like this is
a good discussion for us. There is a lot to unpack here. But I want to start out with
that SPF 25 sunscreen that was really reflective. There’s two major ways
that sunscreens can protect your skin from UV light. One of the ways is by
absorbing that light and turning that
energy into heat. And another way is by
reflecting the light. And what you saw was
clearly more reflection. Now, in the media,
they’re often called physical versus chemical
sunscreens, which is maybe not the best designation. I don’t think it’s the best. Because they
are all chemicals. Maybe it’s a better distinction
to say that the chemical sunscreens are organic, because
they are organic molecules. They have these
chains of carbon. And the so-called
physical sunscreens are inorganic molecules,
things like titanium dioxide and zinc oxide. So they do a bit
more reflection. But they also do
scatter the light. They absorb the light. This chemical versus
physical distinction bothers me, as you know. Because I think it’s
used in a misleading way on a lot of health blogs
and in a lot of media indicating you should
avoid these chemical sunscreens because
they’re chemicals. You don’t like it. I don’t like it. Because they’re all chemicals. Right. Everything’s a chemical. Right. I think there is a deeper
reason why people would say chemical versus physical,
because chemical could describe, by virtue of
its chemistry, that’s how it interacts with the light. Whereas, a physical sunscreen,
by virtue of its structure, is really how it
interacts with the light. You’re right when it
comes to the marketing, people do try to use
the chemical label as a negative term. And I think that it actually
hides an important discussion about the potential
safety issues of what they call chemical sunscreens. So we’re discovering things
about sunscreen ingredients all the time. For example, recent
research has shown that some sunscreen
ingredients– and in particular, some of the
organic sunscreen ingredients– can get into the bloodstream
and into breast milk through your skin, which led the
FDA to recently state that this is a significant discovery that
needs to be considered as we continue to evaluate the
health and safety of sunscreen ingredients. In fact, the FDA just
recently rejected eight new proposed
sunscreen ingredients. Because they felt
there wasn’t enough science to show that these
ingredients were safe. But my question is
that, now that we know sunscreen ingredients can enter
the body through the skin, should we be looking back
at those 16 ingredients? Should we be looking at
them through the lens of the new research and judging
them with the same thoroughness that we’re judging these
eight new ingredients against, for example? What’s surprising to me is
that there is still so much to be learned about sunscreen. I think it’s a little weird
because on the one hand, you’re saying these health
blogs are saying chemicals bad. But on the other,
you’re saying, well, maybe chemicals are bad,
because they haven’t been really tested yet. That’s not why people are
saying that they’re bad. And in fact, some of them
may be perfectly fine, and they get lumped in
with the ones that do have, that do cause skin allergies. Like, to say because they’re
chemicals is the reason, you might lose out
on potentially a ton of great sunscreen
ingredients that are going to be really
effective for protecting the populace
against skin cancer. But people have lumped them
into this chemical category, which really just means
organic molecule category. Maybe we’re going
to find ones that don’t get absorbed into
the bloodstream as readily. You know what I mean? Yeah. There is so much
to be learned. But at the end of the day,
I think, put on the sunscreen. At the end of the day,
do you want skin cancer? Because it is the most
common cancer in the US. You heard it from the man. Wear sunscreen, kids. Oh, yeah, also thank you
for watching this video. And check out Derek’s video,
which is going to be about– The world in UV. Something about sunscreen, but
about everything else, too. Really cool experiments
that we filmed yesterday. Check out the video by the
How to Make Everything guys. They made sunscreen in the end. Did they? Yeah. Awesome. Yeah. I’ll watch that. I will link both of those
videos in the description and at the end of this
video or whatever. Thanks so much for watching,
and happy physics-ing. Thanks to Curiosity Stream for
supporting PBS Digital Studios. Curiosity Stream is a
subscription streaming service that offers documentaries
and nonfiction titles from a variety of
filmmakers, including Curiosity Stream originals. For example, you could
check out Vitamania, a documentary hosted by
Derek Muller himself. The world streaming
premier of Vitamania is on Curiosity
Stream on August 2nd. And Vitamania is all
about the $100 billion vitamin and supplement industry. To learn more, you can go to and use promo code PhysicsGirl
during the sign-up process. It’s cool. You have a tagline. I don’t have a tagline. I know. Yeah, but it’s
happy physics-ing. It’s still pretty
good, though. No one’s going to steal that. Bazinga. You know, someone
tried to steal it once. And I was like, you can have it.

100 thoughts on “SUNSCREEN in UV”

  1. this is actually badass. UV is super damaging in a lot of parts of the world it would be great if sunscreen could be more available in supply worldwide to help lower the incidence of skin cancers. simple stuff like that hasn't kept up with other more urgent meds in the boonies of the 3rd world like mosquito nets and vaccines have

  2. Every time I tell people to wear sunscreen, I ask them, "Remember that sunscreen song?" To which I then send a link.

    Also. I've been testing sunscreens for almost 2 years now in search of the perfect one. People find it a bit weird since I'm a man, but there's totally a market for a non-fussy moisturizing sunscreen. The ongoing debate, especially since that article came out about sunscreen ingredients in your bloodstream is, I think, better classified as MINERAL vs chemical. What you didn't point to in that article was the methodology which included something like having the sunscreen on 75% of your body for 6 consecutive days or something like that. In other words, unless you're a beach bum (in the kindest of words), non-real world testing conditions.

  3. many insects see uv (also shrimp for some reason), and flowers have special patterns that show up in uv to direct pollinators to their nectar. butterflies raised in cages can find artificial nectar if it's in conjunction with some kind of uv reflecting item, like plastic beads. The moral here is if you collect butterflies and don't want to be seen, ๐Ÿ™‚ some sunscreen might help.

  4. So…I've heard of these swimsuits that are made of some kind of special fabric that allows UV rays to pass through it. The purpose of these swimsuits is to allow someone to tan their entire body while still remaining clothed, and not having to worry about tan lines. I'm curious to know if, when viewed through a UV camera, these bathing suits are… I don't know…see through? Invisible on camera? I wonder what would happen.

  5. I realize just now that every summer, without anyone knowing it, im secretly doing blackface … ๐Ÿ˜ฒ

  6. I read or heard that the problem with above 50+ sunscreen, the issue is not that they dont actually block out more UV light, the issue is that regardless of the UV protection factor, your skins oils start to slough off the sunscreen. The issue there is that someone with 100 SPF believes that they have to apply less often than 50 SPF, and that is false because how fast your skin removes the sunscreen, or it gets washed off or rubbed off of evaporates etc, has nothing to do with the SPF factor.

  7. Sounds kinda counter-intuitive that you want to absorb the UV, instead of repel it, when you think about it. Shouldn't we really use something that reflects all the UV light instead of absorbing it? ๐Ÿค”
    EDIT: Hadn't gotten to 5:54 yet. Nice.

  8. Why not show how all the Cancer producing properties enter the blood stream? If you can't put it in your mouth, don't put it in your mouth.

  9. I just recently discovered this channel and this video and and found it awesomely informative. I learned so much from it and I like how the information is broken down so that it's accessible to an average person on the street.

    But… I was also completely distracted by the fact that Dianna and Derek were sitting on the couch with their footwear on. Yes, I realize it's an outdoor piece of furniture and exposed to more dirty elements than a comparable piece of indoor furniture, but even so, seeing "shoes" on the furniture bugged the living daylights out of me. It's a personal picky that is equal parts the buttons my parents installed in me growing up, and the fact that I live in a big city and walking through town, the streets and sidewalks are extra nasty and had visions of that gunk being transferred to the sitting area. I"m sure I'm not the only one. lol So anyways, I had to watch the video a couple of times to get past that and fully get full details of the message <shrugs>
    Love the science and the learning, but please, keep the shoes off the furniture. even outside! ๐Ÿ™‚

    That little rant aside, I hope to see more from the channel that spark my desire to learn more!

  10. Most sunscreens I tested give me headache and burning eyes. And no, I do smear or sweat it into my eyes.

  11. Imagine putting on all those different sunscreens from weakest to strongest (In SPFs) on your arm and sorta blending them and making a gradient tanline that would be so cool

  12. The only use for the UV camera was to spray sunscreen graffiti and look at sunscreen on the skin? Very disappointing. What about putting it on a something transparent to UV and using the camera to see how much was UV was allowed through the sunscreen? I think the camera could have been better used.

  13. Put the sunscreens on a pane of fused silica (UV transparent) and measure the transmission. Nah, that's too methodical and rational.

  14. People are so worried about chemical this and chemical that. You know what else is a chemical? The stuff they pump into you during chemo therapy to treat cancer. That's the stuff I want to avoid.

  15. Great video!!!!! Thank you…but I kept wondering though….about the different SPFs, and how much they can reflect or absorb UV depending on the amount applied….coming from the literature that establishes that the amount needed to really offer the established SPF on label is the determining factor on how effective it is on the claimed protection. It would've been very interesting to see if there is and how much of a difference it makes. Just a though…..thanks!!๐Ÿ‘๐Ÿค—

  16. I'm actually surprised I haven't heard about the sunscreens made from organic chemicals marketed as "organic". Because we all know that "orgainic" means good. As long as your nightshade is organic, it is good for you… Umm…. Wait…

  17. **Sunscreen above SPF 50 uses a chemical SPF, not a mineral SPF (EG titanium/zinc oxide). Chemical SPF breaks down faster than mineral SPF w/ sun exposure and needs to be applied 20 minutes before sun exposure. Chemical sunscreen needs to be applied more often and absorbs UVA/UVB rays while mineral SPF blocks them. Both types of sunscreen should be applied at least every 2 hours and after exposure to water. Mineral SPF is widely recommended over chemical SPF by Dermatologist.

  18. UVb is an absolute need for the human body to make adequate vitamin D to keep you healthy, UVa is not but that is what these screens stop.

  19. Read some pub med, thereโ€™s no proof sunscreen prevents cancer and a lot of proof sunscreen causes cancer. If you want to protect yourself from the sun stop eating seed oils. And if you must use sun screen use a natural zinc. This is more industry shill bs selling you the cure to a problem they sold you previously.

  20. ร really wonder that foots on couche with shoes โ€ฆ for real that rude and ok ist a outdoor couche but , that Looks like never learn that this is wrong , i mean kid know that you dont do that because Mother get Angry …

  21. Funny similar controversy (maybe not true controversy). DEET is a great compound for bug spray, but over 20% has been shown to be potentially toxic for children. But the compounds in "natural" bug sprays tend to be worse than kids than DEET

  22. Diana, If I gave you a huge piece of highly compressed carbonite that took over a million years to make it the densest piece of rock on the planet, would you be my fiancee? No hurry to the alter, we can slow things way down after you say yes. Giggity giggity!

  23. im pretty sure they are dating and they just don't want anyone to know so as to protect their channels in case it doesn't work out.

  24. I thought the SPF meant the amount of time spent in the sun with protection and then after that time, spf 30= 30 mins, you would not be having protection or you should reapply the sunscreen. This was not talked about in the video, maybe it is right and just on the label or something or maybe I have it wrong…

  25. OK! Humans will dip in sunscreen and walk around, cool. How does all the life on planet, plants, animals.. no sun screen and they are fine? or are they also getting affected and no one to help?


  27. Sometimes as an adult one has to learn how to walk again. God our Father the king of Kings has compassion for you and the prayer of your heart reached Him and my heart is touched also. Continue to trust Him. ๐Ÿ™‚


  29. The is a big reason why a higher SPF is better. In the US we have no rating system for UVA rays. The wavelengths that affect DNA, cause wrinkling, destroys collagen and causes cancer. SPF only rates UVB rays that burn. The only guide we have for UVA is an assumed percentage of the SPF.
    In Europe and Asia where the filters available are far superior to US filters they have a PA and PPD rating for UVA.

  30. 30 spf= 97% of rays

    50 spf= 98% of rays

    100 spf= 99% of rays

    Idk if this is all correct but Iโ€™m pretty sure I heard it somewhere haha


  32. The best protection is to go BACK to NORTHERN EUROPE, your ORIGINAL HABITAT and never leave again, remain there

  33. Reason why ppl use chemical sunscreen esp on face bc it isnt as irritating and it doesnt leave white cast, easier to blend. Simple lol

  34. The graph for effectiveness of spf is not linear. Which means that while SPF 100 is better than spf 50, the difference between them is still lesser than that of between spf 10 and 50

  35. It's sunscreen that contributes to skin cancer
    The sun gives life
    When you eat processed food and I'm not connected to nature this song will give you cancer
    You are connected to nature and eat natural foods the sun will never give you cancer

  36. It seems the people in the comments know more about the UV than you do. You must have gotten you degree at the 5&10 cent store.

  37. Spf does not have anything to do with how strong the sunscreen is. It's how frequently you're supposed to reapply the sunscreen. It's meant to be how long your skin takes to burn without anything on it times the number on the bottle is how long you're supposed to reapply the product. It has absolutely nothing to do with the actual strength of the lotion. So therefore anything over the spf 50 is pointless because you're supposed to reapply after that point normally anyway….. PLEASE PLEASE PLEASE pay attention to this comment! The companies trained us about this while i was a beauty advisor at Walgreens.

  38. You also show up as white in the UV spectrum. Wouldn't that mean you're reflecting and not absorbing the UV light ๐Ÿค” There was barely any difference between your skin and the mineral sunscreen.

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