‘Sun Protection Factor’ is ‘a multiplier of the length of time you can spend in the sun without burning,’ explains David Bank, director of the Center for Dermatology, Cosmetic and Laser Surgery. ‘If you could be out for 10 minutes at noon in August before you start to turn pink, then putting on SPF 4 would allow you to stay out for 40 minutes.’ Keep in mind, however, that products are tested under strict lab conditions that don’t perfectly reflect the real world: You may burn faster than the SPF digits suggest.
SPF is only half the story
There are two aspects of ultraviolet (or ultraviolating) light that cause damage: UVB rays, which have a more intense, shorter wavelength, and UVA rays, which have weaker, longer wavelengths. ‘Early sunscreens aimed to protect us from UVB alone, because scientists didn’t realise that UVA did that much damage,’ says Dr. Bank. ‘While those sunscreens were protecting us from burning, we were getting cell damage from the UVA rays.’ This unfortunate oversight may explain why skin cancer rates have surged in the past few decades. And here’s the, ahem, rub: The SPF number on your tube of sunblock still only reflects the amount of protection it offers against UVB rays. The FDA has finally addressed this issue and, in the coming months, consumers will start to see a one through four rating of UVA protection on their sunscreens.
Decode the label
There are two ways that sunblock guards your skin from UVA and UVB rays: chemical sunscreens, with active ingredients like Parsol 1789, Helioplex or Mexoryl, which soak into the skin and absorb certain wavelengths, and physical blockers, like zinc oxide and titanium dioxide, which sit on the surface of the skin and create a barrier that deflects the rays. (The latter ingredients are what gave lifeguards in the 60s their silly white-coated noses, but chemists have since figured out how to make the product invisible.) Zinc and titanium, which appear in most sunscreens that claim to be “natural”, offer a possible solution to any distaste for dubious, potentially harmful chemicals, since they don’t absorb into the skin.
Do I really want green tea in my sunscreen?
In short, yes. Any antioxidant – like green tea, grape-seed oil or beta-carotene – makes a helpful addition. ‘It’s like doubles tennis,’ says Dr. Bank. ‘Your first line of defence is the sunscreen agent – the guy at the net. If it does its job properly, it intercepts UV rays. But some UV light inevitably gets past the sunscreen – over the net player.’ That light creates free radicals, which are high-energy, destructive molecules – like mini-bombs that are extra-damaging to skin cells. The job of the antioxidant is to take the energy off the free radical and absorb the blast so the skin cell doesn’t have to.’
Do it right
In order to get the full protection a sunscreen offers, you have to apply enough of it – a full shot glass for your whole body. Luckily, the uncomfortable greasy sheen that my Coppertone used to leave is no longer an issue – all the sunscreens above felt fairly natural on my skin: I forgot I was wearing them after a few minutes. If you’re using a chemical sunscreen, apply it 30 to 40 minutes before venturing outside. Physical blockers, meanwhile, are effective immediately. Whatever you’re using, re-apply it every two hours (or after 40 minutes of swimming) – active ingredients in sunscreens break down over time. And don’t trust the ‘waterproof’ claims on the label: The FDA banned that word in 1999, since no product is truly impervious to H2O.
The clothes call
Sun-protective threads are scaled in terms of UPF (UV-protection factor): ‘If a shirt is UPF 50, then only one 50th of the sun’s rays are getting through,’ explains Dr. Bank. And what’s the deal with regular clothes? It depends on the type of material, density and colour: ‘Lighter colours attract light, while darker colours absorb it – and therefore block it.’ Go for tight knits: A loosely woven cotton has a lot of spaces through which rays can find your skin. And keep in mind that when clothes get wet, they become more permeable to sunlight. ‘White T-shirts can drop from a UPF 7 to a UPF 2 when they get wet,’ says Dr. Bank. Dark denim, meanwhile, is a UPF of 1,500 or so—though jeans on the beach are arguably more uncomfortable than a body full of slimy sunscreen.