Hi it's me, Michelle from Lab Muffin with more science meets beauty. I keep
coming across recipes for DIY sunscreen so I thought I'd make a video about them.
There are rumours that store-bought sunscreens are toxic and may even be
more harmful than the sun itself. So many people are turning to DIY sunscreens
using what's considered the safest sunscreen ingredient, zinc oxide, commonly
called zinc. The ingredients of a store-bought zinc oxide sunscreen look
something like this in Australia: Active ingredients: zinc oxide 15%. So you'd
think that mixing 15% zinc oxide into a base would give SPF 50, right? And
sunscreen can be quite expensive as well, so it's fantastic for your budget! That's
what people are thinking when they whip up a DIY sunscreen recipe that looks
something like this: Oils, zinc oxide, stir a few times.
Sometimes people even slap an SPF label on it and sell it. Unfortunately this is
a terrible idea. There's a good reason that sunscreen is
treated legally as a medicine. People put on sunscreen that's labelled SPF 30, go
into the sun's cancer-causing UV rays, and expect the sunscreen to protect them.
Because cancer is a pretty big deal, most countries have lots of regulations
around sunscreen. Think about the other things that protect you and your loved
ones from death. Would you put on a radiation suit you found on Pinterest
before going into a nuclear zone? Would you trust a DIY seatbelt? A DIY guide to
surgery? A DIY rollercoaster you found on a blog? (Please don't say yes.) In case
you think skin cancer is no big deal, here are some statistics on it.
2 in 3 Australians have skin cancers by 70. There's one melanoma death in the US
every hour. Your risk of melanoma doubles if you've had more than 5 sunburns.
And daily sunscreen reduces your risk of squamous cell carcinoma by 40% and
melanoma. by 50%.
So now that you know how important sun protection is, how do you make sure your
sunscreen works? Here's where SPF comes in. SPF stands for Sun Protection Factor.
It tells you how much protection from sunburn you get with sunscreen compared
to nothing at all. For example with SPF 30 sunscreen your skin can handle 30
times as much UV before burning, if you apply the right amount. UV changes with
the time of day and with clouds, so SPF testing usees special UV lamps in a
lab. Testing sunscreen on microscope slides is unreliable, so it's tested on
actual human volunteers. 2 mg of sunscreen are applied per square
centimetre of skin for the test. There's also a broad-spectrum requirement in
most places, which means that the sunscreen has a decent level of
protection against UVA. Sunburn is mostly caused by shorter wavelength UVB,
but newer research has found that longer wavelength UVA is also damaging. Both
contribute to skin aging and cancer. Because proper SPF testing is quite
complicated it costs thousands of dollars. There are other regulations
around drugs and that costs even more. That's part of the reason why sunscreen
is expensive.
Another reason sunscreen is expensive is that it's very difficult to make a
product that reliably protects you from the Sun, Unfortunately it's more
complicated than just using the right amount of UV protective ingredients,
Cosmetic formulators consider sunscreen one of the most difficult products to
formulate because changing almost any tiny thing will change the final SPF. The
TGA in Australia states in their testing guidelines the SPF and other physical
properties of the sunscreen are affected not only by the active ingredients
but also by the base. Cosmetic chemists used the amount of active ingredient as
the starting point for a sunscreen. There's still a lot of trial and error
before they can make a sunscreen that works. And it's not just working out what
to put in the other 85%. There are a ton of factors to consider when making an
effective sunscreen - there are a whole text books written on it. Here are some
of the other factors that will affect SPF: distribution of the active in the
sunscreen; interactions between different ingredients; the pH of the sunscreen; how
the sunscreen's been mixed; how the sunscreen applies on skin; how the
sunscreen dries on the skin; separation and degradation on the skin; settling and
degradation in the bottle over time. The amount of active ingredient is only one
tiny part of the puzzle. Let's look at just one factor, pH. Zinc oxide dissolves
below pH 7,and when it's dissolved it won't give any protection. Your skin and
sweat are both below pH 7 so the pH of the sunscreen will drop as you're
wearing it. Proper sunscreens are formulated to avoid this problem. You can
see here the different SPFs you get with similar amounts of zinc oxide. 15%
zinc gives one sunscreen SPF 50 plus. 19% zinc gives another sunscreen SPF 15.
The BASF calculator, a tool that cosmetic chemists use as a starting
point for formulations tells us that 20% zinc gives us SPF 8 or 13. So there isn't
a straightforward relationship between the amount of active ingredient and SPF.
Let's say you've managed to get exactly the same ingredients as a commercial
zinc oxide sunscreen and you're ready to mix them together. You still won't
necessarily be able to make a sunscreen that works because, just like cooking, the
sunscreen ingredients need to be mixed in the right way.
Zinc oxide is a particularly annoying ingredient to use in sunscreens because
it's notorious for clumping up. This is a problem because bigger particles mean
poorer coverage. For example, if you have a cherry, it'll cover the area the size of
the cherry. But if you smash it up into juice you can use it to cover a much
larger area even though you've used the same amount of cherry. Again, 15% zinc
oxide doesn't always give the same protection. Here's a table from a zinc
oxide supplier showing the SPF values you get from two different sizes of
particles. Even with the same percent zinc oxide the SPF halves when you
change the particle size. Most DIY sunscreen recipes don't recommend the
right size of zinc. But even if you buy the right size of zinc, it doesn't mean
it'll work because when zinc oxide clumps up it turns into bigger particles. How
can you stop the zinc oxide from clumping? In commercial sunscreens zinc
is usually coated with ingredients that make it clump less, but DIY sunscreens use
uncoated zinc oxide because the coatings aren't "natural". Even when coated, zinc
oxide requires industrial homogenizers, which are super powered electric mixers,
to spread the particles out. Both of these sunscreens look even when you apply
them, but when you look at them under a microscope you can see the tiny holes
where you'll get no protection. In fact you can get worse than no protection
because oils can increase UV damage. Zinc also clumps up and settles over time,
even in some commercial sunscreens that have passed SPF testing. So even if you
somehow managed to get the DIY sunscreen to work one time, the sunscreen
probably won't be the same when you use it the second time. It can also clump up
as you apply it. Again the clumping might not be visible. So in summary, a
sunscreen's effectiveness doesn't depend on the amount of a single ingredient it
contains. It doesn't even depend on the amount of all the ingredients that
it contains. The process of making the sunscreen
makes a big difference too, and shaking it in a jar or using an electric mixer
won't cut it. I mean, this bowl contains the same cake ingredients as this
delicious delicious batter. But it won't turn out the same when you bake it.
Official SPF testing uses human volunteers, but that doesn't mean testing
it on yourself is a good idea. The test needs to be done in a reliable way that
will reflect whether it will be effective for most people in real life.
Just like how my grandma smoked like a chimney, had one kidney, and lived till
ninety, a sunscreen that you wore while not burning isn't necessarily an
effective sunscreen. Were there any clouds that day? What was
the UV like at that time of year? What was the time of day? Do you have sun
resistant skin? Did you go into the shade? How often were you facing so that your
skin was in the shade? How much did you sweat? Did the sunscreen brush against
clothing? There are too many variables so if it worked, all you can say is that it
worked for you in that exact situation once. In proper SPF testing they control
for all these variables. Sunburn is also only one of the effects of UV.
Sunburn mostly happens due to UVB but UVA causes cancer, pigmentation
and wrinkles. Even if you don't get burned using a DIY sunscreen, you're potentially
exposing yourself to some serious UVA damage that you won't know about until
many years later. Sunscreen may be expensive but it's expensive because
it's effective, and it's much cheaper than skin cancer.
There aren't any studies showing that sunscreen chemicals cause more harm
than good. They definitely protect against skin
cancer and aging, according to the most recent studies. There's some speculation
that sunscreen ingredients can cause endocrine disruption, but the in vitro
and animal studies that found that use way way more than you'd ever be exposed to.
There's also concern about nanoparticles, but the current evidence
shows that they don't pass through the skin's surface. Allergic reactions are
real risk though, so make sure you patch test if your skin is sensitive. Aside
from that, the UV protective benefits of using a proper sunscreen outweigh the
risks.
Unfortunately DIY sunscreen isn't better than nothing. First, people stay in
the sun longer if they think they're protected, so you'd get more sun damage
overall. Secondly, oils don't give good sun protection. In fact, oils can
sometimes increase sun damage. If there are microscopic holes in your sunscreen
you'll have no protection there, possibly worse than no protection.
Finally zinc oxide itself can be a problem.
A lot of DIY recipes tell you to use uncoated zinc oxide because it's
supposedly "more natural". But uncoated zinc oxide is photoreactive.
This means that when it's exposed to UV, it will react with other substances to
produce free radicals, one of the big causes of skin damage. Coating the zinc
oxide stops this from happening. While we don't know whether the amount of free
radicals has a big effect on the skin, you're potentially causing extra damage. By
wearing DIY sunscreen you might actually give yourself more sun damage
than wearing nothing at all! Keeping in mind the scary skin cancer stats I
showed you earlier, this is pretty darn scary. DIY sunscreens are a bad idea
because it's incredibly unlikely that you've managed to make something that
can reliably protect you from cancer-causing UV rays - and DIY sunscreen
can potentially expose you to more damage than nothing at all.
Save DIY for things that don't run the risk of giving you cancer. If you're
still worried about the dangers of sunscreen, then don't use them and practice
some avoidance. Stay in the shade or wear sun protective clothing. Or you can
choose to only buy sunscreens containing ingredients you regard as safe. Don't
repost DIY recipes and encourage other people to try them, even if they work for
you. You don't want to be responsible for their skin cancer. If you see people
selling DIY sunscreen illegally, you can report it via the links I've provided in
the caption. I hope this video made sense to you. If you enjoyed it please like it
and share it! You might also like to check out my blog, watch the other videos
on my channel, and subscribe :)