Finally: This Is the Real Difference Between Sunscreen and Sunblock

Sunscreen vs. sunblock

Basically, sunscreens absorb and sunblocks sit on top of the skin. The easiest way to remember the difference between sunscreen and sunblock is by the end of the words. As Ashley Magovern, MD, a board-certified dermatologist, explains, sunscreen will absorb and scatter sunshine before it can penetrate the skin.

Sunblock, on the other hand, sits on top of our skin and blocks the sun's rays by reflecting them. Though both methods provide protection, they aren't created equal, if you ask the experts.

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Sunblock is more effective

If you read the back label of your sunblock and sunscreen, you'll be surprised at just how different they are. Blair Murphy-Rose, MD, FAAD, a board-certified dermatologist at Laser & Skin Surgery of New York, says sunblock often has zinc oxide and/or titanium dioxide. This allows it to become the physical barrier between the skin and the sun's harmful rays.

Typically speaking, Dr. Murphy-Rose says sunblock is more effective than its sister sunscreen. She says zinc oxide and titanium dioxide are currently the only ingredients that meet the Food and Drug Administration's requirements to be labeled GRASE (Generally Recognized as Safe and Effective).

"The active ingredients in sunblock are also thought to be safer for the environment," she says. "Coral reef destruction is a major environmental concern, so it is important to choose a sun protectant that contains reef-safe active ingredients."

Sunscreen contains chemicals such as avobenzone, octocrylene, homosalate, octisalate, octinoxate, and oxybenzone, among many others. Though these do provide the sun protection we need, Dr. Murphy-Rose says the jury is still out on how potentially damaging they could be to our bodies with consistent use. Also, sunscreens often need to be reapplied more often and given more time to seep into our pores.

"Because sunscreen does not create a physical protective shield, it does not tend to provide as much protection against many sun-induced conditions like pigmentation changes and rosacea compared to sunblock," she says. "Chemical sunscreen ingredients are more likely to elicit allergic reactions than are zinc or titanium."

Sunblock is thicker

When you're using a sunblock or mineral sunscreen, you may notice it's more difficult—if not impossible—to rub in completely. This is because its ingredients create a thick formula to provide that much-needed physical barrier. While it can be frustrating with squirmy kids and when you'd like your sun protectant to be invisible, Zain Husain, MD, FAAD, a board-certified dermatologist, says it's better to layer it on thick and reapply than to skimp.

Use of the term 'sunblock' is no longer permitted by the FDA

Even if sunblock is more effective in terms of ingredients and use, you likely won't find products using the word. How come? According to Adam Mamelak, an Austin, Texas-based dermatologist, the FDA outlawed the use of the word "sunblock" in 2011 because it felt the phrase gave consumers a false sense of security when spending time outdoors.

"According to their reasoning, topical preparations can help protect you from the harmful effects of ultraviolet irradiation. However, nothing can completely 'block' the sun," Dr. Mamelak says. "The FDA, therefore, did away with this term and it is no longer allowed to be used with labeling of approved products."

The same is true with sweat-proof and waterproof products, which are now called water-resistant since, technically, they are only effective for a period of time, not forever. "The idea here was not to give consumers the false sense that they are protected for an entire day at the pool. Rather, the cream has to be reapplied," Dr. Mamelak says.

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Focus on these keywords

Since everything will mostly say sunscreen these days, to find a sunblock, consult the back label to look for zinc oxide and/or titanium dioxide. Once you spot one or both of those ingredients, check the front and make sure it's at least an SPF 30 or higher, says Brendan Camp, MD, FAAD, a double-board certified dermatologist. Make sure the sunscreen also features keywords like broad-spectrum (which means it protects against UVA and UVB rays) and water-resistant (which means it will be effective for 40 to 80 minutes in the water before you need to reapply).

While sunscreen is essential, Dr. Camp says it should only be step one before braving the sunny day ahead: "It is also recommended to use UV-protective clothing, hats, and sunglasses to defend against UV radiation directly from the sun and also from reflective surfaces, such as sand, snow, and water," he says.

When in doubt? Remember: Too much sun protection is never a bad thing.