Sunscreen is a year-round mandatory step in your routine, but summer means stepping up your SPF game. More time outside and longer days mean more sun exposure, and you’d be forgiven for having a couple of questions about how best to protect yourself. Let’s be honest: social media is flooded with SPF myths, from bad sunscreen science and dangerous DIY recipes competing with real information. So, what’s the truth? Your burning SPF questions, answered by the experts!
Featured Experts
- Kelly Dobos is a cosmetic chemist
- Joel Schlessinger, MD is a board-certified dermatologist based in Omaha, NE
- Janine Hopkins, MD is a board-certified dermatologist with practices in Southlake, TX and Monroe, LA
How Are Sunscreens Tested?
For an SPF to achieve a rating, it has to be tested on humans. These in vivo studies are a measurement of how well the sunscreen protects against sunburn, caused primarily by UVB rays.
“The test uses reddening of the skin, referred to as erythema, to determine the level of protection by comparing areas of skin exposed to artificial sunlight with and without sunscreen,” explains cosmetic chemist Kelly Dobos. “That’s why the test requires subjects with lighter skin tones, as it’s much harder to recognize erythema in dark skin tones, and there’s a risk of delivering very high doses of radiation to darker skin tones to get to a sunburn condition.”
To get certified as “broad spectrum,” a sunscreen must also provide protection against UVA rays.
“For this test, we shine UV light through a thin layer of sunscreen on a plastic plate and measure how much light gets through, and this tells us how far the protection extends into the UVA range,” Dobos explains.
Why Shouldn’t You Decant Sunscreen?
Decanting, or transferring sunscreen to a different container, isn’t recommended. Exposure to light and air causes the formula to degrade, and new packaging could be harboring microscopic contamination or even mold spores. Ultimately, the packaging that sun protection comes in is designed to keep the formula stable and effective.
Plus, as Dobos points out, you’re wasting your time for an amount that doesn’t provide enough protection. “The amount of product TSA allows does not make sense for someone using sunscreen as recommended,” she explains. “You’re meant to be using one ounce every two hours or after swimming/vigorous exercise, and the TSA limit is only 3.4 ounces, so that only covers you for a few hours. My recommendation is bring a larger bottle in a checked bag or buy some sunscreen when you get to your destination.”
Are Chemical Sunscreens Safe?
Chemical sunscreens work by converting UV rays into heat and then releasing that heat. They take about thirty minutes to become active, which means you need to apply them before going into the sun. Chemical sunscreens use active ingredients like homosalate, oxybenzone, octinoxate, avobenzone and octocrylene among others.
“These are chemicals that operate like a sponge—they permeate the skin upon application and absorb UV rays where they then convert the rays to heat and release them from the body,” Omaha, NE dermatologist Joel Schlessinger, MD says. “This entire process helps prevent the UV rays from causing sun damage or sunburns in the skin. Sunscreen manufacturers may recommend that chemical sunscreens need time to fully take effect, but that isn’t how most people use them. I would prefer a sunscreen at any time, even if it isn’t given the full 30 minutes before sun exposure.”
These chemicals have developed a bit of a bad reputation they don’t deserve. “Chemical sunscreens are not inherently bad,” Dobos explains. “Some studies have shown these sunscreen ingredients can be absorbed through skin after repeated use, but there is no evidence that these levels cause harm in humans.”
And we know that these chemicals are effective and dermatologist-recommended.
Are Mineral Sunscreens Always a Good Choice?
In recent years, mineral sunscreens have taken center stage as the safe and effective option for sun protection, minus the chemicals.
“Yes, I’ve definitely seen an increase in interest in mineral sunscreens over the past year,” explains Southlake, TX dermatologist Janine Hopkins, MD. “And given how much skin sensitivity we’re seeing right now, those formulas are what I recommend to help keep skin from reacting. You want to look for a mineral sunscreen that prioritizes clean, safe ingredients alongside the actives.”
But these formulas have challenges, from a notorious white cast to issues with spreading product evenly.
“Zinc oxide and titanium dioxide are insoluble powders, so they have to be suspended in the base formulation,” Dobos explains. “This makes it harder to ensure consistency across batches and uniform application on the skin. In contrast, chemical filters are typically soluble in the formulation, allowing for more consistent distribution.”
Why Is the U.S. so Far Behind on SPF?
Around the world, sunscreen formulations are getting more advanced. But at home, U.S. sunscreens have a very strict process to pass in order to make it to market.
“In the 1970s, the U.S. FDA reclassified sunscreens from cosmetics to over-the-counter (OTC) drugs, which subjected them to much stricter regulations,” Dobos says. “This shift was really rooted in a desire to protect public health, recognizing sunscreens as essential tools in cancer prevention.”
This change means active ingredients for sunscreen have to go through a drug-level approval process, and the FDA requirements for safety data means that ingredient manufacturers have a lot of hoops to jump through. And plenty of them don’t find it worth the effort.
“In fact, all but one of several manufacturers that were pursuing approval of new active ingredients have effectively abandoned efforts,” Dobos says. “This caution by the U.S. FDA is not fundamentally bad—it reflects a commitment to public health. But the lack of flexibility and slow adaptation to scientific advancements has left U.S. consumers with fewer, less elegant options.”
