Hi everyone, I’m Picky Expert Dr. Mara Padilla Evangelista-Huber.
I’m a board-certified dermatologist and a certified dermatopathologist with a masters
in clinical trials.
Today, we’re going to talk all about sunscreens.
Let’s start the discussion by talking about why we need sunscreen in the first place.
Sunscreens protect us from the harmful rays of the sun, particularly ultraviolet radiation.
There are actually three types of ultraviolet radiation: UVA, UVB and UVC.
UVC, thanks to the ozone layer, doesn’t really penetrate into the Earth’s surface.
So the focus is on UVA and UVB protection.
UVB has shorter wavelengths than UVA.
UVB penetrates the epidermis, which is the upper layers of the skin, and it is the main
UVR responsible for sunburn.
It also can cause damage to our skin cells, which if not repaired, can lead to skin cancer.
UVA, on the other hand, can penetrate deeper into the skin, where it reaches the dermis,
and that’s actually where you find the collagen in your skin, which is why UVA is primarily
responsible for the signs of photo-aging, which manifests in the skin as fine lines,
wrinkles, roughness and pigmentations like sun spots.
UVB is usually called the burning rays because they’re responsible for sunburn, and UVA
is usually called the aging rays because they’re primarily responsible for aging.
But the reality is both UVB and UVA contribute to aging, sunburns and also skin cancer.
So that’s why it’s really important that your sunscreen protects from both UVB and
UVA.
So for the next question: how do sunscreens work?
The active ingredients in sunscreens are the sunscreen filters.
The only two inorganic filters are zinc oxide and titanium dioxide.
All the rest are organic filters.
Just a quick review of what you read on sunscreens.
When you see the term SPF, or Sun Protection Factor, this actually refers more to the UVB
protection of the sunscreen.
This doesn’t really tell us a lot about how much protection the sunscreen provides
against UVA.
Other parameters describe UVA protection such as the PA system, the PPD system, Boots Star
Rating, or the term Broad Spectrum Sunscreen.
Nevertheless, whatever the labeled protection in the bottle, this is only achievable if
you actually apply the sunscreen correctly.
And what does this mean?
This means you’re applying the right amount, and you’re also putting an even, smooth
layer on the exposed layer of your body.
Based on laboratory studies, you have to apply two milligrams per centimeter squared of sunscreen
to achieve the protection stated in the label.
This roughly translates into one fourth teaspoon for the face, one half teaspoon for the face
and neck, one half teaspoon for each arm, and one teaspoon for each leg, the front of
the torso, and the back of the torso.
In reality, however, only one half or one fourth of this recommended amount is actually
applied by the user.
And like I said, that really impacts how much protect you get, so it’s really important
that A) you apply the right amount and B) you apply it the right way.
It’s very important to have an even, smooth layer of sunscreen where you apply it.
So it’s not just enough that you have the right amount.
You should also apply it as evenly as possible.
And why do you have to do that?
The skin is ridge-like.
It has hills and valleys, so if you apply too thin of a layer, you might cover the valleys
but you haven’t actually adequately covered the hills.
In fact, in laboratory settings where they test for the SPF, care is really exercised
to make sure that the sunscreen is applied as evenly as possible, but we know, in reality
we don’t really take that much care in applying our sunscreen.
But it does really matter because it will equate to better protection.
Sunscreen can be likened to a paint job over skin, where a single layer, especially on
a rough surface, again like the skin, isn’t really enough.
But, another layer, or even thicker layers, will give better coverage.
It is going to cover all of the hills and valleys adequately, so that an even layer
is achieved.
Another thing to remember is that sunscreen needs time to be an even layer on top of skin.
So this is actually the reason we tell you to wait 20 or 30 minutes before you go outside
or before you put makeup on top of your sunscreen because it takes for sunscreen to set.
It takes time for paint to set.
So that’s the reason why you need to wait, and not because you want the sunscreen to
activate.
Another question I get a lot from my followers is: “Do you really need to reapply sunscreen?”
Sunscreen sits on top of the skin, and because the skin is a pliant, moving organ, naturally,
the things that are on top of it also tend to move.
And remember, we really need an even layer of sunscreen for it to work effectively, but
if that layer moves around, then that even layer isn’t really achieved anymore.
That is why we want to reapply.
So the reasons for reapplying sunscreen are: #1) To compensate for potential, initial under-application.
#2) To replace sunscreen that might have been removed by movement, sweat, swimming, sand,
friction with clothing or anything that might have brushed against the skin.
I want to remind everyone that sunscreens are not complete sunblocks.
Some UV radiation can still penetrate into the skin.
And as I have mentioned, the efficacy or effectiveness of your sunscreen is very user-dependent.
In many cases, you are not really able to achieve the right amount or the right application
to get that labeled protection on the sunscreen.
Therefore, it’s really important to do other sun protection measures.
For example, avoiding direct sunlight as much as possible, seeking shade around the middle
of the day, using protective clothing or protective accessories such as sunglasses, wide-brimmed
hats.
There are clothes with UPF ratings that you can also use.
And actually, if you think about it, they might even be more effective than sunscreens
in the sense that you don’t have to remember to use them.
You don’t have to remember the right way to apply them.
You also don’t have to remember to reapply them, which is why it’s probably best to
do everything that you can.
All the sun protection measures that you can to keep your bases covered.
And what’s the best sunscreen?
It’s the sunscreen that you like and will use every day.
But some guidelines that are good to remember are that it’s SPF 30 and above, it’s broad-spectrum,
meaning it covers for both UVB and UVA, it’s water resistant, it’s suitable for your
skin type, whether you’re oily or you’re dry, it’s easily spreadable because that’s
actually how you get a nice, even layer, and it doesn’t irritate your skin.
If you have sensitive skin, it’s likely better to go with the inorganic filters like
zinc oxide and titanium dioxide.
The same recommendation also goes for pregnant women, breastfeeding women and children.
Unfortunately, these sunscreens also tend to leave a white cast, and if this is a concern
for you, it’s probably better to go with sunscreens with organic filters.
There are sunscreens that have a mixture of both, and you can choose whatever fits you
best.
Apply your sunscreen about 20-30 minutes before going out or applying makeup.
It goes after all of your skincare products, but before your makeup.
So the order is: skincare, sunscreen, makeup.
Reapply sunscreen every two hours.
However, whenever you’re just indoors, I find that a single application is enough,
especially if you’re away from windows and direct light.
Throw away your expired sunscreen.
The filters are not going to be effective beyond the expiration date.
Store your sunscreen below 30 degrees Celsius.
When you’re outside, keep them under the shade, and don’t store them in your car.
And lastly, evaluate your sunscreen.
Is it doing its job?
Are you still getting sunburned?
Are you getting new pigmentations?
Does it feel nice?
Does it look right?
Because you have a lot of sunscreen options, and if you’re not happy with your sunscreen,
by all means, find another one because the most important criteria in sunscreen selection
is something that you like and will use every day
If you want to know more about the science of skincare, you can follow me and Picky on
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Thanks for watching!
Bye!