How does sunscreen work? Sunscreen can sometimes seem a bit complicated, but it’s not once you get to know it… Here, we answer the most frequent questions we receive about it––so just consider this your little SPF cheat sheet of sorts, should you ever need it.
1. What is SPF?
Let’s keep this answer as simple as possible: SPF stands for Sun Protection Factor, which is the measure of protection from the sun’s UVB (burning) rays.
2. What do SPF numbers mean?
The numbers on your tube of sunscreen indicate how long the sun’s UV radiation would take to burn your skin when using that product exactly as directed. For instance, SPF 30 would take you 30 times longer to burn than if you weren’t wearing any sunscreen at all. Each number will also protect your skin from a certain percentage of the sun’s UVB (burning) rays. Just to be clear though, SPF numbers are based on different situations and skin types (i.e. if you’re outside swimming or if you have particularly oily skin, the SPF number will not last as long). Also, this number is not infinite; the protection only lasts for two hours and then you’ll have to reapply.
See here for the breakdown of SPF numbers:
- SPF 15 – Blocks 93 percent of UVB rays
- SPF 30 – Blocks 97 percent of UVB rays
- SPF 50 – Blocks 98 percent of UVB rays
But what numbers should you gravitate towards, you might ask? Well, any dermatologist will tell you that any SPF between 30 to 50 is your sweet spot. Anything below 30 (including SPF 15, listed above) won’t protect you from enough of the sun’s UVB rays, and anything above 50 gives people a false sense of all-day protection. This SPF will also only protect you from less than one percent more of the sun’s UVB rays, while exposing your skin to a much higher concentration of active ingredients that can be irritating in the process. And whether or not you choose SPF 30 or 50, remember to apply and reapply it generously.
P.S. We also only believe in broad spectrum SPF, as it’s the only type of SPF that will protect your skin from both UVB and UVA (aging) rays. More on those – and reapplication – below…
3. How does sunscreen work?
Sunscreens work by using certain types of actives (either mineral or chemical) to absorb the sun’s damaging UV rays. Chemical SPF actives include avobenzone, homosalate and octocrylene, while mineral actives include zinc oxide and titanium dioxide. These two mineral actives will also help protect your skin by reflecting some of the sun’s UV light, in addition to absorbing it.
4. What is UV Radiation exactly, and what’s the difference between UVA and UVB rays?
UV stands for “ultraviolet,” and exposure to ultraviolet radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV radiation, but tanning beds can also mimic this form of light and cause skin cancer and other kinds of skin damage.
There are two main types of UV rays: UVB (burning) rays and UVA (aging) rays. We talked a little bit about UVB rays above, but these are the are the ones that are typically associated with the beach. In addition to skin cancer, they can lead to sunburns.
UVA rays are the ones responsible for aging, fine lines, dark spots and all those little things we don’t like about our skin (along with skin cancer). Plus, they shine at about the same intensity all year round and penetrate through things like clouds and windows. About 95 percent of the UV energy that reaches the earth is composed of these rays. Learn more about them – and why you need to wear sunscreen every day, even when you’re indoors – here.
In order to keep your skin safe from these UV rays, you’ll want to wear a broad spectrum sunscreen – just keep scrolling for more info on that…
5. Why is broad spectrum SPF the be-all, end-all?
The SPF number on any tube of sunscreen only designates the level of protection it’s giving your skin from the sun’s UVB (burning) rays. You’ll want to make sure that the label says it’s a broad spectrum sunscreen, which means it will protect you from UVA rays. This way, you’ll be protected from the sun’s rays when you’re outside and inside. Thankfully, all of Supergoop!’s sunscreens are broad spectrum. Fun fact: They also all help protect your skin from infrared rays that can cause free radicals, which leads to skin dehydration and tissue damage. And some even protect your skin from blue light, which is the light emitted from electronic devices, like computers and phones.
6. How much sunscreen do I need to apply daily?
You’ll need one-half of a teaspoon (about a nickel-sized dollop) for your face and neck, and one ounce (a shot-glass-full) for your entire body. And while these are the general guidelines, we also suggest applying it as generously as you feel like you should and then immediately repeating, as studies show that people apply about half as much as they ought to. Also make sure that every visible part of your skin gets covered with a nice layer of SPF!
Layering different kinds of SPF products will also help ensure that you’re getting enough protection. One of our favorite “SPF routines” involves Superscreen (our daily moisturizer), then Unseen (our invisible makeup-gripping primer), then CC Cream (our color-correcting cream that provides nice coverage from imperfections), then Defense Refresh (Re)Setting Mist (our makeup setting spray).
7. What’s the deal with sunscreen and reapplication? And if I wear sunscreen all the time, am I missing out on getting a healthy amount of daily vitamin D?
Any type of sunscreen (chemical or mineral) will naturally break down on your skin when exposed to light over a period of time. This happens because once you put SPF on your skin and your skin’s exposed to the sun, it will begin breaking down the actives that provide protection. Plus, other things like running around, touching your face and sweating will contribute to SPF degradation.
The rule of thumb is to reapply your SPF every two hours – or more if you’re swimming or sweating – to stay protected all day long. And if you’re wondering how to reapply sunscreen easily, especially over makeup, we’ve got you. Just click here.
As for vitamin D, here’s the truth: Vitamin D and sunscreen are not mutually exclusive. It’s a myth that wearing sunscreen all the time can interfere with you getting the amount of vitamin D your body needs. The amount of vitamin D you need is only made during your first ten minutes out in the sun, which isn’t long at all. You’ll most likely get the right amount every day because of factors like not applying your sunscreen as generously or as much as you should be, and because of the fact that no SPF number protects your from 100% of the sun’s rays (remember, SPF 50 blocks you from 98% of the sun’s rays).
8. Do I need to be more cognizant of wearing SPF when I’m on a plane or visiting the mountains?
Yes, yes, yes! Think about it: When you’re on an airplane, you’re much closer to the sun, which means you’re even more likely to be exposed to UV damage. The same is true when you’re spending time at higher elevations, like in the mountains. The actual statistic is that with every 3,000 feet you climb in elevation, UV levels will increase by 10 to 12 percent. In fact, an hour’s worth of sun exposure on a plane gives your skin as much UVA exposure as laying for 20 minutes in a tanning bed!
While you don’t need to wear a higher SPF number at higher elevation, you will want to wear a generous amount of sunscreen and reapply it more diligently. You already know that your sunscreen actives will naturally degrade over time, and when you’re that close to the sun, you don’t want to play any games! So keep that SPF handy when you’re on the plane, skiing or hiking.
9. How do I know that sunscreen is going to work?
Great question! We take efficacy really seriously here at Supergoop! and we spend months – sometimes years – testing products before launching them to make sure they not only feel good on your skin, but also – and most importantly – live up to their protection claims. Furthermore, we’re the only brand that actually publishes or efficacy reports for each product on our website – because what’s the point of sunscreen if it doesn’t actually work? Check them out for yourself here.
10. OK, give it to me straight…what’s the difference between chemical and mineral sunscreen?
Here we go…! Chemical sunscreen uses organic actives, like avobenzone and homosalate, while mineral sunscreen uses inorganic actives, like zinc oxide and titanium dioxide. Both types of actives absorb UV rays to some extent, and mineral ones can also block a percentage of them.
Chemical SPF allows for major innovation, like light textures and clear formulas for deep skin tones and breathable formulas great for activity, while mineral SPF usually works best for those with sensitive or acne-prone skin and when you’re spending a good amount of time indoors. It’s also nice to use mineral actives when formulating makeup-friendly sunscreen.
Want to know even more about the difference between chemical and mineral sunscreen, and which type is best for you? Just give this video a watch to learn more.
+Have more burning questions about SPF? Or still wondering: how does sunscreen work? We’ve got the answers! Just drop your question in the comments below and we’ll answer it for you!