What SPF do you need?
The SPF on a sunscreen tells you how long it will take for the sun’s UV radiation to cause your skin to redden. So with SPF 30, it takes 30 times longer to burn than if you aren’t wearing any sun protection. Any amount of SPF is helpful, but the number tells you how often you need to reapply it. Dr. Chan recommends no less than SPF 30 for everyday purposes, but if you’re going to be out in the sun consistently, you’re better off with something closer to SPF 50.
How often should you apply sunscreen?
Daily, and probably in greater quantity than you suspect. Not to belabor the point, but sunscreen is a daily necessity — not just one reserved for beach days. “Whether it’s sunny or overcast, your skin is still getting exposed to the sun’s UV rays which can contribute to sunburns, hyperpigmentation, and photodamage. Sunscreen is also something you need year-round, not just in the summer,” says Dr. Obioha.
Furthermore, sunscreen is not to be applied lightly. Dr. Chan says most people use about 10 to 25% of the sunscreen they should. “When you’re applying in a thin layer you’re actually getting a fraction of the SPF protection, “she says. For that reason, aim for a density of two milligrams of sunscreen per centimeter square. “An easy way to measure it is two finger lengths per body area: Two finger lengths for the head and neck, two finger lengths for the front of the body, two finger lengths for the back of the body, each of the legs and arms.”
Reapplication is key if you’re in the sun for an extended period of time. Reapply every two hours for the best protection. “Degradation of sunscreen is dependent mostly on UV exposure, so if you are not inside for most of the day and are not exposed to sunlight, the sunscreen you apply in the morning may still have some protection in the afternoon when you leave the office,” Dr. Chan explains. However, if you’re, say, biking to work in a sunny locale like Southern California, you’ll want to reapply when leaving the office to make sure you have adequate protection.
Otherwise, if you’re spending a day outside or engaging in a water-based activity, be sure to slather on a new layer of protection as soon as you get out of the water, she says — “even if you’re wearing water -resistant sunscreen.”
How do you apply sunscreen with makeup?
“I recommend applying sunscreen after moisturizer and before makeup,” says Dr. Chan. She suggests waiting a few minutes for the sunscreen to absorb into your skin before applying your makeup. In order to keep your makeup look intact when reapplying, you can reapply with an SPF powder, spray, or apply a liquid SPF to a beauty blender (mixed with your foundation if you prefer) to smoothly add on top of your existing face makeup.
Which sunscreens are reef- and ocean-safe?
People should be aware of the impact their sunscreen has on marine life, and prioritize the products that allow them to protect their skin while respecting the environment, says Cinzia Corinaldesi, a professor of applied marine biology at the Polytechnic University of Marche in Italy and of applied marine ecology at the International Master of Marine Biology (IMBRSea) who has a focus on anthropogenic and climate change impacts on biodiversity and ecosystems.
The main issue is with ingredients called UV filters, which include oxybenzone, octinoxate (ethylhexyl methoxycinnamate), benzophenones, methylbenzylidene camphor, and octocrylene, although other things like preservatives (eg, parabens) have also been linked to a negative effect.
“Research studies have demonstrated that several sunscreen products are harmful for a wide range of marine organisms, including algae, zooplankton, sea urchins, and corals,” she explains, pointing in particular to the UV filters.
In an older study Corinaldesi was part of, researchers found that some UV filters, even in tiny amounts, bleached corals in different tropical locations across the world. “UV filters such as oxybenzone and octinoxate have been repeatedly investigated in different ecosystems and marine species,” she says. Mineral filters, too, including zinc, are also being studied for their potential reef harm.
As of January of 2021, oxybenzone and octinoxate have both been banned in Hawaii, and we mostly recommended products that are free of these harmful chemicals.
The environmental impact of beauty products should play an important role in making informed purchases. This could mean paying closer attention to the ingredient lists, as Corinaldesi recommends, or using outside, independent research, such as from The EWG, to vet products. The final decision should come down to a product that becomes a part of your daily routine. “The best sunscreen is the one that you’ll use,” Dr. Chan states plainly.