I’m currently writing this intro in an almost unbearable state of schwitz! It’s that time of year again where you think twice about the necessity of any errand, if it means going outside during the day.
Which is to say, it’s HOT! Most days are really bright and sunny and for people like me (proactive anti-agers) it can be a real bitch to feel protected from the sun.
It’s a constant struggle between wanting to protect my skin from the sun, but also be as comfortable as it’s possible for me in this heat. Seriously, just THINKING about putting on sunscreen breaks me out into a sweat!
My sunscreen practices have been a bit lax these past couple of years, so I went on a refresher deep dive on everything sunscreen.
I wanted to find out just what is important in sunscreen use (and what’s bullshit) and how I could maximize my protection, without falling into hysterics. If that sounds good to you too, let’s go!
Why is sunscreen important?
The official sunscreen recommendations you get from dermatologists probably sound positively neurotic to the average person. Most of us think of buying and using sunscreen only in the summer, when we’re planning to go to the beach, or pool, or camping. But the fact is we should probably all be using a more of it year-round.
Sunscreens (just like clothing, hats, and sunglasses) protect from the sun’s rays. These rays are very beneficial to us on the one hand, but incredibly destructive on the other. Usually, it’s down to the amounts of exposure and the intensity of the rays, but among the negative effects of UV radiation are:
- Sunburns: they have a cumulative effect on DNA that mutates it and increases the chances of developing skin cancers and other skin diseases. Mostly caused by UVB
- Skin cancers: mostly caused by UVB
- Skin aging and degradation: 80% down to UV radiation – mostly UVA
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How sunscreens protect from the sun
Sunscreens work by absorbing and scattering the UV (ultraviolet) radiation from the sun.
You have UVA, UVB, and UVC, which relate to different wave lengths. (*)
- UVC is blocked completely by the ozone layer (no worries there)
- UVB is mostly blocked – about 5% makes it through the atmosphere
- But the bulk of UVA (about 95%) hits us like a hammer
Sunscreen was first created to protect from the obvious signs of UV radiation – the burning of the skin, i.e., sunburn – which is actually caused by that tiny percentage of UVB that makes it through. That’s actually what SPF is about.
What is SPF? How does it protect from the sun?
SPF (Sun Protection Factor) is a measure of UVB protection only!
It’s calculated by dividing the amount of time it takes for skin with sunscreen to start to redden from sun exposure, by the amount of time it takes for the skin to start to redden without sunscreen. (*)
So the SPF value does not relate to UVA protection at all.
The UVA wave lengths actually penetrate the skin a lot deeper than the UVB ones. They’re responsible for 80% of skin aging and the production of oxidative stress in the body.
In order to make sure that your sunscreen is protecting you from both types of UV, make sure that it says it’s either “broad-spectrum”, or that it has another form of UVA sun protection factor stated, like PPD (Persistent Pigment Darkening), or PA (Protection Grade of UVA), or the UVA seal, if you’re in the European Union.
How much sunscreen do you need?
All SPF is tested in the same way, by applying 2mg per cm² of exposed skin. To get the SPF you see on the bottle, you’ll have to be applying those amounts.
Now, just how much is 2mg of sunscreen per cm² in terms of actual product volume, you ask? This will of course depend on the extension of skin – some people are bigger and taller than others.
Aside from calculating how many cm² your face or body have, there’s no way to give an exact number. However, the official general recommendations for adults come to approximately:
Or about 1 full shot glass for your whole body, including the head.
Those are of course measuring spoons and NOT kitchen spoons. If that looks like a lot of sunscreen – it is! Which leads us into our next point.
How often should you reapply sunscreen?
Now, even if you’re applying the recommended amount, and you’re out and about, you should reapply the sunscreen every 2 hours or so.
If you’re at the beach, in contact with sand and water, or being physically active, it’s even recommended that you reapply every 90 minutes.
This is because sunscreen will rub off with clothes and sand, it will sweat off as you exercise, and it will wash off in the water.
It’s recommended that you reapply within 1 hour after the first layer, just to make sure that the amount on your skin is closest to the actual amount needed to achieve the SPF. (*)
Also because the skin is not a completely flat structure – it has tiny bumps and dips. So applying more than one layer will get you closer to the intended SPF.
Now, if you decide to wear sunscreen indoors (see further down) you don’t need to be reapplying that often – maybe just 2 or 3 times throughout the day. Definitely reapply if you’re going outside.
What SPF should you get to really protect from the sun?
Generally, the fairer your skin, the higher the SPF you should get. Nevertheless, official recommendations in most places are to shoot for at least a 30 SPF, regardless.
This is in part due to the fact already mentioned that practically no one is applying the correct amount of sunscreen, so you’re not really getting what it says on the bottle. (*)
Putting on higher SPFs is a way to increase the protection, if you’re not putting on enough. (*)
Mineral vs Chemical sunscreen
The dilemma is real. Just what is the effing difference between mineral and chemical sunscreens, and which one should you use to best protect from the sun?
To put it simply, mineral (or physical, or inorganic) sunscreens are the ones that use zinc oxide and/or titanium dioxide as active ingredients. Both are minerals.
Chemical (or organic) sunscreens are all the others. They have synthetic active ingredients, like avobenzone, oxybenzone, homosalate, octisalate, octinoxate, octocrylene, among others.
It used to be that experts believed that a mineral sunscreen would reflect the UV rays, while chemical sunscreens would absorb them, turning them into heat.
But there’s enough data now to confirm that both types absorb and turn the UV rays into heat, to a large extent. AND that both types do reflect a minor portion of the UV radiation. (*)
While mineral sunscreens are considered safe for the general population, even in large amounts, chemical sunscreens have been shown to be absorbed into the bloodstream.
Not only that, they seem to accumulate in the body with use. There was a recent study that confirmed these chemicals do reach the safety threshold level in the body that the FDA has set, which means that they now require further testing to prove that those levels are safe for human health.
It doesn’t prove that chemical sunscreens are not safe, it only quantifies the amounts that are absorbed into the bloodstream with use, and because those amounts reach that maximum established by the FDA, it now requires further testing.
So which type of sunscreen is better?
That will depend on your personal preferences, skin sensitivity, comfort level with the idea of chemicals being absorbed, and your general goal in using sunscreen.
Mineral sunscreens
These are good for people with sensitive skin, since they hardly ever cause any reactions (unless they have perfume in the formulation, which might).
Also they’re usually perfect to apply around the eye area, which is more sensitive in general.
If your skin is on the oilier side, mineral sunscreens might help, since both zinc and titanium are powders. Although this depends a lot on the formulation itself – a lot of mineral sunscreens are thicker.
They offer great UVB protection and zinc oxide in particular also broad-spectrum UVA protection. (*)
The major downside of physical sunscreens is, of course, the dreaded white cast – almost impossible to escape it. This makes it less user friendly, since you’re more likely to not want to use it on a regular basis.
Chemical sunscreens
These generally offer higher protection against UVA (if they are labeled as broad-spectrum) and are generally more subtle on the skin.
This means, you’re not going to get that awful white cast, so it’s more doable on a daily basis. It’s hands down much easier to make it a daily part of your skincare routine.
The downside is of course the uncertainty over the effect of the chemicals that are absorbed – we just don’t know. Oxybenzone is the most vilified of the lot, but all the chemical sunscreen agents studied do enter the bloodstream.
Can sunscreen cause cancer?
As mentioned above, all science has been able to establish is that these chemicals are absorbed into the body enough that more research is needed.
It’s also true that certain chemicals that appear in sunscreen are also present in other hygiene and cosmetics products. That’s the more worrying aspect perhaps. We’re surrounded by toxins, not just in the products we use, but also in the air, in the water, in the food we eat. Bioaccumulation is a real thing.
Cancers and autoimmune diseases have been on a constant rise for decades and there’re just too many variables to be able to say for sure what is causing what. Quite likely, it’s a mix of factors and products.
For instance, you may have heard that skin cancers – the very thing that sunscreen use is meant to prevent, primarily – have gone up in the decades that sunscreen has been in use.
Some people argue that maybe the absorption of the chemicals in sunscreen is causing this rise. That’s a possibility, or a factor, but there are other possibilities as well.
For instance, it’s been established that people wearing sunscreen, especially a higher SPF sunscreen, will generally engage in more risky behavior. They’ll stay out in the sun longer than they otherwise would, they won’t be so prone to seek shade, or wear sun protective clothing, such as long sleeves or even hats. Because they have sunscreen on, they think they’re safe. (*)
If we consider that most people are not applying sunscreen the way they should to get the SPF they think they’re getting, and the fact that they don’t reapply as often as they should (if at all) … It could be a recipe for disaster in the long run.
Can sunscreen cause acne?
They don’t by definition cause acne, but of course it will depend on your skin and the particular product formulation you choose.
If you have acne-prone skin and you choose a thicker, oilier, or physical sunscreen, they might clog your pores. Especially if you’re not removing the sunscreen correctly.
Look for more lightweight formulas and make sure to remove your sunscreen well with an oil-based, cream or balm cleanser every night.
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Does sunscreen expire?
Yes, sunscreen does expire. It’s important to check the expiration date on the bottle and make a mental note of it. If you’re not sure, don’t use any sunscreen beyond 2 years since buying it.
Ideally you should be using it up relatively quickly and so replacing it every month/couple of months/few months depending on the size of the bottle and your lifestyle.
It’s important to not use expired sunscreen, because beyond the expiration date the manufacturer cannot assure it will protect from the sun.
The ingredients will degrade over time, causing one of two things: loss of efficacy (no longer protecting you from the UV radiation) and skin irritation.
This is much more likely with chemical sunscreens, but it can happen with physical ones as well. When the ingredients deteriorate they can wreak all kinds of havoc with your skin, so best not to chance it.
Also take into account how you’re storing your sunscreen! Don’t keep it in hot or too cold a temperature, because both can compromise the stability of the ingredients.
Ideally you should be keeping it in a dry, cool environment, protected from direct light (ironically).
Do moisturizers and makeup with SPF protect from the sun?
Generally speaking, probably not. The reason is again down to the actual amounts used.
People usually don’t put on that much moisturizer and they’re not likely to reapply it throughout the day. The same is true with makeup. They definitely won’t cover their ears or back of the neck, for instance.
There’s also the matter of real-life coverage as well, if the product is something like a mineral powder. There’s a very good video of a journalist applying different types of products with SPF under a UV camera, that shows you the actual UV protection coverage of that product on the skin.
One of the products is a makeup powder with SPF and there was barely any coverage at all. Moisturizers and makeup with SPF are more useful as layering products, to put on under or on top of your sunscreen and help reinforce the protection.
Remember, we don’t generally apply enough sunscreen to be getting the SPF stated on the bottle. So every other bit helps to stay protected from the sun.
Related content: How To Layer Skincare (Like You Know What You’re Doing!)
Do you need sunscreen indoors?
The honest answer to this is: it depends. Windows effectively block UVB rays (the burning rays), but not all the UVA rays.
This means that if your primary concern is preventing a sunburn or skin cancer – you don’t really NEED to wear sunscreen indoors.
However, if you’re very proactive about preventing skin aging or hyperpigmentation then you might want to seriously consider it.
Having said that, it also depends on the amount of light you’re exposed to indoors. It actually depends a lot on things like size of windows, sky view from those windows (whether or not the sky is blocked by things like curtains, shades, or trees), the UV index where you live at any particular time, how close to the windows you sit, etc.
There’s a very good video by The Lab Muffin explaining it all in detail and even giving you a way to actually calculate the amount of sky view you’re exposed to. I recommend it if you want to dig (a lot) deeper.
But basically, the closer you are to the window, the more you should consider using sunscreen. The fewer buffers you have between you and the sky view from your windows, the more you should consider using sunscreen.
Having said all of THAT, the blue light that comes off our screens (computers, phones, TVs, etc) also seems to negatively affect collagen (the way UVA does).
You can actually block that blue light by using products with iron oxide. So, your basic tinted sunscreens or foundations should do the trick, if you’re really gung-ho about anti-aging.
Does sunscreen block vitamin D synthesis?
The answer to this is yes AND no.
The UV wave length necessary to synthesize vitamin D is particular to the UVB spectrum. So in theory, if you block UVB, which is the main or, let’s say, classical function of sunscreen – to block the rays that burn the skin – you would in fact be blocking the rays you need to make vitamin D.
However! That seems to be the case ONLY if we apply sunscreen the way it was intended. Meaning, if you’re indeed applying 2mg of sunscreen per cm² of all exposed skin and you’re reapplying that sunscreen every 90 minutes to 2 hours, you might indeed be preventing the body from being able to synthesize vitamin D.
But because pretty much no one actually applies sunscreen correctly, studies on this have shown that vitamin D production is actually not compromised in real-life settings.
The fact is, even if we are applying the right amount, we usually will miss areas. Could be the ears, or parts of our neck, or any nook and cranny. And even if we are reapplying, it’s usually not as frequently as we’re meant to. And even if we are reapplying that often, it still does rub off or sweat off.
The importance of the UV index
Having said all of the above, it’s important to remember that UV intensity will vary according to time of day, latitude (geographical location), and season. And the ability to synthesize vitamin D from it will also vary according to individual genetics, skin color, and age.
People who live in more northern climates will be exposed to a lot less UVB and people of darker skin color have more “built-in” protection to begin with. Vitamin D insufficiency, or downright deficiency, is a worldwide phenomenon.
Since vitamin D is so important to human health, it’s worth weighing out the risks in your particular situation. Especially, let’s say, if you’re using sunscreen every day and indoors, because your main goals are the anti-aging benefits. Or if you have darker skin and are living in a more northern climate.
If the UV index outside is below 3, some official bodies do recommend you go outside without sunscreen, because the health benefits far outweigh the risks in this situation. It’s important to protect your skin from the sun, but also not live in fear of it.
How to protect yourself from the sun effectively (sun safety tips)
- sunscreen + makeup with SPF
- moisturizer with SPF + sunscreen (+ makeup with SPF)
- by applying a second layer of sunscreen about 20 minutes or so after the first layer
- by using very high SPF sunscreen (even the ridiculously sounding SPF 70 or 100)
- If you’re outside you should still favor the shade (especially between 10am and 4pm)
- Wear protective clothing (with SPF or made of tightly woven fabric) and hats (as wide-brimmed as possible)
- Don’t stay out in the sun longer than you otherwise would, just because you put on sunscreen.
Sunscreen use, clothing, and shade effectively protect you from the sun. They’re really all you need to prevent major damage, like skin cancers.
The nuances, headaches, and hair-splitting really comes when your main concern is anti-aging.
Trying to balance broad-spectrum, year-round sun protection, physical comfort, natural and beneficial sun exposure, enjoyment of life! You’re just going to have to decide for yourself what’s more important to you, what you can live with and without.
I hope you got some useful information about the different types of UV and how you can protect your skin from them. And how to best go about sun protection, depending on what your major concern might be.
The truth is that the experts don’t have all the answers and everyone interprets the data available through their own lens. Like always, do the best you can!
If you have any comments or question, let me know.
