Sunblock vs. Sunscreen: What’s the Difference and Which One Should You Use?

Summer is almost here, which means it’s time to stock up on sunscreen…or sunblock. Wait, what’s the difference, exactly? We brought the sunblock vs. sunscreen question to two dermatologists to get the full scoop on what both terms refer to and how to find the formula that’s best for you. Read on so you can catch some rays in the safest way possible.

• Dr. Marisa Garshick, MD, FAAD is a leading board-certified dermatologist serving patients throughout Manhattan, New York at MDCS Dermatology: Medical Dermatology & Cosmetic Surgery, as well as an assistant clinical professor of dermatology at Cornell - New York Presbyterian Medical Center.
• Dr. Rebecca Marcus is a board-certified dermatologist with nearly two decades of experience specializing in medical, surgical and cosmetic dermatology. She’s also the founder of Maei MD, a dermatologist-approved line of skincare products.

Before we get into the differences between these two products, we should mention that the term “sunblock” is a dated one, since the FDA no longer allows for its use on labels as the descriptor “may overstate the effectiveness of completely blocking UV rays and give consumers a false sense of reassurance,” explains Dr. Garshick.

As such, what was once called sunblock now falls into the sunscreen category—specifically mineral-based formulas. This is as opposed to chemical-based products, which is what most people mean when they say sunscreen. Confused? Read on.

The mineral-based stuff was once called sunblock because it works by creating “a physical barrier that reflects UV rays away from the skin,” says Dr. Marcus, adding that it “provides broad-spectrum protection…[and] starts to work immediately upon application.” That’s also why sunblock is known as “physical sunscreen.” The most common ingredients used in mineral-based sunscreen include titanium dioxide and zinc oxide. And because this formula “blocks” the suns rays from penetrating the skin, it is not absorbed by the skin and, thus, very often leaves behind a visible white residue.

Dr. Marcus tells us that chemical-based sunscreens, on the other hand, boast a “formulation that absorbs UV rays before they can penetrate the skin [and contains] active ingredients…that convert UV rays into less harmful forms of energy such as heat.” These chemical formulations also provide broad-spectrum (i.e., UVA and UVB) protection, but they do need to be absorbed into the skin in order to be effective and it is recommended that they be applied 15 to 30 minutes prior to sun exposure, so the active ingredients have time to work.

Both chemical and mineral-based sunscreens are highly effective at blocking UVA and UVB rays and providing broad-spectrum protection when used properly and reapplied every two hours. That said, Dr. Garshick points out that mineral-based sunscreens are “especially good for people with sensitive skin as they tend to be less irritating,” mostly on account of the fact that they merely sit on top of the skin as opposed to sinking into it, as with chemical formulations.

Dr. Marcus echoes this recommendation with regard to sensitive skin types and adds that, in general, mineral-based sunscreens “provide slightly broader spectrum UV protection, though both types are highly effective.” Both experts agree that the most important thing is to pick a sunscreen that’s SPF 30 or higher, wear it every day and, as previously mentioned, reapply it every two hours.

We hinted at this already, but your sunscreen choice might be influenced by your skin type. Indeed, the experts say that sensitive skin benefits from mineral-based formulas, while the transparent finish of the chemical stuff might be preferred by folks with darker skin tones and less sensitivity. Beyond that, some other factors to consider are the duration of sun exposure—the longer you will be outdoors, the higher the SPF should be—and whether or not you will be sweating a lot or going in the water, in which case water-resistant sunscreen is recommended. (Both mineral and chemical sunscreens are available in water-resistant formulas, but even water-resistant sunscreen should be reapplied every 40 to 80 minutes.)

Another pro tip, courtesy of Dr. Marcus: “Powdered sunscreen, can be a useful formulation to be applied to the scalp,” particularly for those with thinning hair—just don’t rely on powdered sunscreen as a primary layer for other parts of the body, as it doesn’t stick to the skin as well as lotion or cream formulas do.

Both mineral (aka sunblock) and chemical sunscreens are highly effective when it comes to protecting your skin from sun damage, but sensitive skin will likely fare better with the former. Either way, remember to wear SPF 30 or above every day and reapply it on the regular.