Sunblock and Sunscreen Have Key Differences—We Asked Derms to Break Them Down

By now, you must be aware that sun protection is the most important part of any skincare routine. But while this fundamental fact is clear, choosing an SPF can be a bit confusing, especially considering there are two basic types of sun protection products: sunblock and sunscreen. Although both names are used interchangeably, there are some key differences between what a sunblock does and what a sunscreen does that may make one better for your skincare needs. 

We asked four industry experts—board-certified dermatologists Dendy Engelman, MD, Corey L. Hartman, MD, Elyse Love, MD, and clinical facialist Kate Kerr—to shed some light on the great debate of sunblock versus sunscreen. Keep reading to learn the difference between the two.

What Is Sunscreen?

Sunscreen, also known as "chemical sunscreen" or "chemical SPF," contains several chemicals that absorb UVA and UVB rays and transform them into heat through a chemical reaction which is then released, explains Engelman. Fellow INCI-philes who study ingredient lists will be familiar with some sunscreen chemicals, including cinnamates, salicylates, octocrylene, and ensulizole, which block UVB rays, and benzophenones, anthranilates, avobenzone, and ecamsule, which block UVA rays.

The key to a sunscreen working is its absorption. Kerr says that sunscreens tend to have a thinner texture that penetrates the skin without leaving a greasy residue or white film, which some (but not all, as you'll see) sunblocks can tend to do, making them ideal for those who have a multi-layered skincare routine. However, because sunscreens are partially absorbed by the body, Engelman says it's important to apply them at least 30 minutes before sun exposure. And because sunscreens tend to last longer than sunblock, you don't need to re-apply them as frequently.

What Is Sunblock?

Sunblock, which is commonly called "mineral" or "physical" SPF, works by forming a "mineral barrier" on the skin which blocks the absorption of UVA and UVB rays, according to Love. Zinc oxide and titanium dioxide are two of the most common minerals used in sunblocks.

Since it doesn't need to absorb to work, Engelman says sunblock is effective more or less right away. However, this also means it washes away more quickly, so you'll need to reapply often, especially when swimming or doing intense physical activity that results in sweating. 

How to Pick the One for You

The official differences between sunblock and sunscreen go well beyond what's inside, which may make it easier for you to choose which is best for you. Here are a few things to consider:

Skin Sensitivity/Conditions

Kerr notes one main reason people may choose sunblock over sunscreen is that sunblock can be less irritating to those with sensitive skin. With that said, she adds that it's rare to find people with true allergies to sunscreen and that it's more likely that their skin is sensitized from skincare; therefore, putting any kind of chemical on top has the possibility to be irritating. 

Kerr says those with melasma may also want to consider sunblock over sunscreen. "Melasma is not only activated by the sun but also heat, so sunscreen that's converting the sun's rays into heat can actually cause melasma. I recommend physical sunblocks in that case." 

Texture

Sunscreen is popular due to its lightweight texture, which can range anywhere from a barely-there gel to a thick, luxurious cream, all with the ability to blend well into the skin and sit comfortably between skincare and makeup. 

The same can almost be said about sunblock, but its high mineral content can leave a white cast behind. "Sunblock technically provides more protection than sunscreen, but it can appear white depending on the formulation," Kerr says. However, Hartman notes that this could be to your advantage: "Physical sunscreen or sunblock may be more difficult to apply elegantly, especially to darker skin tones, but they give you a good idea of how much coverage you're getting. Even the ones that disappear give you a flash of color or iridescence, so you know you've got enough coverage in the right areas." 

If you think sunblock might be better for you but are afraid you'll come off looking like Uncle Fester, fear not. Love says many new sunblock formulations use micronized minerals and work similarly to chemical sunscreens, AKA with a thinner texture that won't leave a white cast. She also points out that many SPF products on the market today use a mix of both mineral and chemical UV filters, providing the best of both worlds. 

Environment

It is also important to consider the environment you will be in when choosing between sunscreen or sunblock (Yes, even if you're indoors, you should be wearing sunscreen). If you will be swimming or having increased physical activity that will cause sweating, sunscreen is the best pick, as it absorbs quickly, and the time you need to reapply is less (sunblock washes away easily). On the other hand, if you are going to be outdoors for a prolonged period, sunblock is a better option as it sits on the skin's surface for better protection. Regardless of your pick, both products should be applied more than once throughout the day.

How to Read the Label

According to our experts, there are three key things to look for on the label of your sunblock or sunscreen purchase: 

High Sun Protection Factor (SPF)

"When looking for sun protection, it should be broad spectrum with an SPF of at least 30," Love says. She adds that SPF 50 and above is better for high sun exposure and those with sun-sensitive conditions, such as hyperpigmentation or lupus. And if you're extra and want to go even higher, don't bother; as Hartman says anything above SPF 50 is superfluous because after 50 the change is small. So the moral of the story is: Keep the SPF between 30-50, and you'll be fine. 

Water-Resistance

This is usually a given for most formulations nowadays, but choosing a formula labeled "water-resistant" means it should hold up well through everyday wear and tear. However, if you plan on swimming or sweating, Kerr says you'll want to reapply at least every 40 minutes to ensure your skin remains protected. She also notes that if you don't like to reapply, opt for a formulation dubbed "super water-resistant," which means you can reapply every 80 minutes.

Antioxidants

Whether springing for sunblock or sunscreen, Engelman recommends looking for formulations that also contain antioxidants to help protect against oxidative damage from environmental aggressors as well as the sun. "Sunscreen ingredients won't do that alone, and you can still incur oxidation when you're protecting against the sun," Kerr adds, "so the combination of antioxidants and sunscreen agents should form the basis of your daytime protective routine."

The Final Takeaway

Love says it best: “The most effective SPF is the one you use.” Sun protection is the most vital element of skincare, Hartman emphasizes, not just for those with sun-sensitive conditions like rosacea, but for all of us, as it can act as an important tool in preventing skin cancer as well as helping to ward off signs of premature aging, discoloration, hyperpigmentation, and sagging. Finding the best SPF product for you takes time, patience, and experience, and armed with the knowledge we’ve just revealed; you can shop smarter for this daily skincare essential.