How Does Sunscreen Work?

The sun is the science-backed external-aging culprit. In fact, it is such a significant culprit that this type of aging is called photoaging. It has been extensively linked to premature fine lines and wrinkles, texture changes, leathery appearance, pigmentation, and downright DNA damage. And yet for some of us (we’re included), we can’t help but want that golden, healthy tan. It doesn’t help that sunscreen isn’t the prettiest of formulas—gooey, white, heavy, greasy, tacky, and it’s even got that signature scent. 

Applying this on the beach makes you think more of that uncle with the shiny white nose who always reeks of sunscreen than the glamorous Miami beach life. But it’s just a matter of finding your perfect sunscreen match. In the long run, better sunscreen habits lead to better skin. It’s the true anti-ager! Here, we’ll make sure you’re getting proper protection with a formula you love. Let’s rekindle your love for sunscreens.

Why Use Sunscreen?

For the laziest of skincare users out there, if there’s just one thing you should do, it’s sunscreen. Below are the reasons why you should use sunscreen.

1. Protect us from skin damage

Let’s all remember that the sun is a giant nuclear reactor that emits energy across a wide spectrum, including visible light, infrared (heat), and ultraviolet. Among the three types, ultraviolet is the main type of radiation responsible for causing skin damage, ultimately resulting in premature photoaging.

The sun emits three types of UV rays. It’s helpful to know the difference, as products will often refer to the different types.

UVC: The shortest of the three wavelengths. Luckily, this one gets filtered out by the atmosphere, and thus we can rest easy and ignore it. (Yay!)

UVB: The mid-length wavelength, UVB makes up 5% of the UV that reaches our skin. Because of a shorter wavelength in comparison to UVA, this only reaches the epidermis. UVB is responsible for sunburns and delayed tanning, and is the main culprit of skin cancer.

UVA: The longest of the three wavelengths, UVA makes up 95% of the UV that reaches our skin. UVA can reach all the way down to the dermis and is responsible for deep photoaging and enhanced skin cancer development. We always remember the two as B is for Burns, A is for Aging.

2. Protect us from skin cancer 

UVB is the main culprit that causes sunburns and, eventually, skin cancer. Its short wavelength means it packs enough energy to directly damage your skin cells and even DNA. This is why if you get a sunburn more than five times, your melanoma risk doubles.

Other than direct damage, UVB and UVA can also cause damage by triggering free radical development. The dreaded free radicals are reactive molecules that unselectively attack your skin cells, proteins, and even DNA, causing long-term damage.

3. Prevent premature aging 

Aside from skin cancer risks, sun exposure is also the major culprit of skin aging. Ultraviolet damage causes everything that you don’t want: sagging, rough texture, leatherlike thickness, hyperpigmentation, wrinkles, dullness, and more. As the sun causes damage to the skin, your own fibroblasts are triggered as an inflammatory response and will start to break down your collagen. 

As another defense mechanism, your skin also thickens, and hyperpigmentation pops up from an overproduction of melanin packets. Dry, dull, rough textures and wrinkles develop from long-term damage. Even that golden, healthy tan is a sign that your skin is defending itself against sun damage. In fact, UV damage is such a significant factor in premature skin aging, there’s a term dedicated to it: photoaging.

Hopefully, we haven’t scared you into retreating underground. Ultimately, we just want to emphasize good sunscreen habits. Sunscreen is a key player in a solid routine and will save you a lot of money on products and procedures in the long run. In fact, that’s why we consider sunscreen the ultimate anti-aging product!

How Does Sunscreen Work?

Sunscreen protects your skin by absorbing harmful UVA and UVB rays so your skin doesn’t have to. While many believe that sunblock actually physically blocks the skin from the sun, instead, it generally absorbs the UV rays and dispels the resultant small amount of energy as heat. It’s important to remember that because sunscreens protect you from skin cancer, they are heavily monitored and regulated by the FDA. In fact, this is why you’ll see sunscreen labels that have a drug facts section so you won’t have to search for the active ingredients from a sea of ingredients, like other products.

When you’re hunting for your sunscreen love, there are three important factors to check off: UVB protection (SPF), UVA protection, and texture.

UVB Protection, AKA Sun-Protection Factor (SPF)

First, SPF is not on a linear scale. It might be tempting to think an SPF 30 sunscreen must offer twice the protection of an SPF 15, but that’s not how SPF value works. SPF 15 actually means that with proper application, it only lets 1/15th, or about 7%, of UVB through. 

This means that an SPF 15 sunscreen blocks roughly 93% of UVB, while an SPF 30 sunscreen blocks about 97% of UVB. Definitely not “twice the protection.” Fun fact! This is why the claim “SPF 100” is banned in the EU, for the misleading insinuation that it can block 100% of UV light. What does this mean practically? For daily use, we recommend choosing a product between SPF 30 and SPF 50 to hit that sweet spot that balances between sufficient protection and a pleasant texture.

UVA Protection

SPF only covers part of the equation, since it addresses just the UVB portion of the rays. You also need proper protection from longer-wavelength UVA rays; these don’t burn skin, but actually penetrate deeper into the skin, and are the main culprits behind photoaging. In the US, look for the words “broad spectrum” on your sunscreen to make sure it’s tested for UVA protection as well.

SPF is fairly universal, but you’ll see different labels for UVA protection around the world. Japan uses a PA system, ranking UVA protection from PA+ up to PA++++. This system is also used in other countries worldwide. In the EU, to get a UVA label, the sunscreen has to have around the same protection level as a PA+++ sunscreen. In a nutshell, this is yet another reason why US sunscreens are a bit behind the times.

Above All Else, Texture Is King

As chemists, we want you to know that formulating sunscreens is a royal pain in the butt. They throw every challenge at formulators, and it really shows when you try to use them. Sunscreens can often end up feeling greasy and heavy, and make you look mime-worthy, with a white-cast finish. Despite all the benefits in protecting your skin, sunscreen isn’t an easy product to incorporate. Hence that is why we want to emphasize that sunscreen texture is king. Remember: For the entire body, you’ll need about a shot glass’s worth of product, and for the face

you’ll need about 1⁄4 teaspoon (roughly the size of a quarter) to get proper sun protection. So, keeping that dosage in mind, the more powerful sunscreen will be the one you’re willing to use every day and happily reapply every two hours. So, don’t spend the time, effort, and emotional despair fighting with yourself to use an absurdly high SPF. The good thing is, gone are the days that you have to use that sunscreen goop—there are options! So, let’s go through the formats and find your sunscreen love!

How To Choose Sunscreen?

Sunscreen is that finicky product that’s a must-use but unfortunately has all sorts of texture and application issues. It can often be too greasy, shiny, smelly, or tacky, or make you look like a ghost. And while you may want to try to aim for the highest SPF possible, we recommend finding sunscreens that you can tolerate and don’t mind applying daily. A lower SPF that you apply daily will always be more powerful than the high SPF you only apply every once in a while. 

There are generally seven sunscreen formats you will find in stores:

  • Lotions & fluids: These two will be your bread and butter. Textures will vary wildly, but this is where paying attention to ingredients can help you narrow your choice. (For help with selection by ingredients, go to page 90.)
  • Oils: Great for beach days, or to leave a nice glow. Like other oil products, not the most travel friendly; prepare for some oil stains.
  • Sprays: Refreshing and great to reapply. It’s important to note that when sprays are tested, they are often sprayed onto the hand and then applied onto the skin surface to achieve a proper amount of sunscreen and an even film.
  • Powders: These are not our product of choice, since it’s very hard to understand how much powder you need to ensure you’re getting proper protection. That being said, there are some days that dusting a layer of sunscreen over your makeup is simply the best option.
  • Sticks: Incredibly travel friendly. Useful for lips as well, but can get greasy.
  • Hybrid moisturizers: The best format for lazy folks that don’t want too many layers. Be sure you apply enough of the product—it’s important to remember you’re applying based on the required sunscreen amount and not the moisturizer amount.

To troubleshoot and narrow your sunscreen hunt, there are four general areas you can focus on:

  1. Chemical vs. mineral: Sunscreen filters are divided into two categories: organic (chemical) and inorganic (mineral) filters. While chemical sunscreens are liquid filters that only absorb UV, mineral filters are powders that mainly absorb but can also reflect and disperse UV rays. Chemical sunscreens happen to have a better texture and less of a chance of leaving a white cast. But they aren’t for everyone, as they can be a source of irritation for some. To make a decision here, it’s important to get to know your ingredients. 
  2. Skin type: There’s no doubt that oily/acne-prone skin types really struggle with the greasy sunscreens. We recommend looking to Asian and EU brands for lighter textures. The truth is, the US is quite limited in the approved sunscreen filters we can use, which means the sunscreens with the best textures are often sold outside of the country. In fact, we’ve often found that sunscreens with octinoxate tend to be lighter—just don’t use them when you’re swimming near the Great Barrier Reef. Otherwise, minerals can be hit or miss. If you’re trying to go mineral, zinc oxide is the safer bet here. To avoid the white cast, use chemical sunscreens—otherwise, it may be time to go look for nano versions of these mineral suncreens.
  3. SPF Value: We typically recommend using anything from SPF 30 to SPF 50. We find that SPF 50 is a sweet spot between good protection and a lighter texture. But there are times when an SPF 30 is more ideal. If you’re struggling with the white cast, texture, or sensitivity, we want to reemphasize that a sunscreen you’ll apply more often will always be more powerful than a rarely used SPF 50 you hate. Remember, texture is king.
  4. To layer, or not to layer?: Sometimes layering can’t be helped. If you plan to layer, do what you can to preserve the sunscreen film and ensure good protection. Make sure sunscreen is the last step in your routine, and allow enough drying time between your moisturizer and sunscreen.

For those lazy folks, all-in-one moisturizer with SPF could be your solution. This will definitely ensure that there’s no interference with the sunscreen film, but be sure you’re applying enough, and reapplying as if it were a sunscreen and not a moisturizer.

A serious word of warning: Avoid concocting homemade sunscreens.

Sunscreens are considered to be OTC products under FDA regulation —what this means is that anything you find on store shelves has been tested for efficacy. A homemade sunscreen recipe often uses zinc oxide, an effective broad-spectrum UV filter. 

However, without a proper formula and the right manufacturing equipment, the DIY brew might not disperse the filters properly in an even film, leaving you with patchy, lackluster sun protection. We have seen plenty of “safe,” “chemical-free” sunscreens sold at hipster markets that are questionably preserved and already starting to separate into multiple layers. Skin cancer is no joke!

Leveling Up Your Sun Protection

Love the great outdoors? Well, slathering sunscreen over your entire body isn’t the only option you have! You can further protect yourself with physical gear.

UV-rated clothing: Fun fact! Sun-protective clothing gets tested for sun protection, too, and gets a UPF rating. This is a number that indicates both UVA and UVB protection. The UPF rating means that, of a given amount of UV, only one part gets through. For example, UPF 10 allows one part in 10, UPF 20 would let through one in 20, and so on; the higher the UPF number, the better the protection. This is important for extensive outdoor time!

Sunbrellas: We often hear questions like, “If I sit under an umbrella and don’t apply sunscreen, I should be protected, right?” Funny enough, someone actually compared sunscreens to sunbrellas in a clinical test. Johnson & Johnson did a clinical study in sunny Texas that looked at just that. They had people either apply sunscreen or sit underneath an umbrella. They found that those who sat underneath the umbrella experienced more tanning and sunburns than those who just used sunscreen. Why? Even when you sit in shade, your body is still being exposed to UV, since UV is reflected off surfaces like sand and water. So, to sum up: Being in the shade of a beach umbrella may help, but it’s not fully sufficient sun protection.

FAQs About Sunscreen

Q: The sun scares me. Do I need to use SPF 100?

A: Generally, if you’re looking for extra protection, SPF50 or 50+ is all you need. At that point, you’re already able to block over 97% of the sun’s rays. Anything more means you’ll have to come to terms with a much heavier, greasier texture that often leaves a white cast. We’re all about compliance here. Wearing a sunscreen that you like daily will always be more powerful than wearing an SPF 100 whenever you can tolerate it.

Q: Do I need to reapply sunscreen at the end of my workday even though I was only in the sun for my ten-minute morning commute?

A: Sunscreen doesn’t work like batteries, where you have a reserve of sun protection. The sunscreen film is meant to only hold up for two hours, and that’s it. Definitely reapply sunscreen for your after-work commute.

Q: How should I layer my sunscreen?

A: Make this the last step of your routine. Applying anything over it really runs the risk of interfering with the sunscreen film and thus diminishing sun protection.

Q: How do I reapply sunscreen with makeup?

A: Great question that comes with a not-so-great answer. Sunscreen powders have been formulated because of this problem, but we don’t actually recommend using them. It is very difficult to quantify the proper amount of powder sunscreen. Instead, we would consider a sunscreen face spray over powders. But the optimal solution would be to use a CC or BB cream instead of foundation.

Q: I’m worried sunscreens are the source of my breakouts!

A: Seek out better textures—the European and Asian formulas are lighter!

Q: I only used my sunscreen once, but it’s expired. Can I still use it? It feels like such a waste to throw it out.

A: Don’t do it! Sunscreen formulas are finicky enough to formulate already—when it’s time for it to go, it’s gotta go.

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