The sun has given us so much. Flowers for example. Also sunsets, vitamin D and the 2002 Sheryl Crow hit Soak Up the Sun.
And yet, despite its brilliant generosity, humans must also diligently protect themselves from the sun, otherwise its ultraviolet rays can wreak havoc on our soft, fallible bodies. One of our most powerful defense mechanisms? SPF products.
SPF, or sun protection factor, is a measure of how well sunscreen protects our skin from the sun’s rays, especially the UVB rays, says Dr. Heather Rogers, a board-certified dermatologist and founder of the Seattle-based practice Modern Dermatology. This protection helps protect sun seekers from skin cancer and premature aging, Rogers explains.
While sunscreen is plentiful in pharmacy aisles and beach bags, many people don’t apply it properly, experts say.
And the consequences are dangerous. Skin cancer is the most common form of cancer according to the United States American Academy of Dermatology (AAD). In Britain, the number of cases of melanoma, one of the most serious forms of skin cancer, will reach a record high in 2023.
“The risk of melanoma doubles with just five sunburns,” Dr. Matthew Block, medical oncologist, and Dr. Tina Hieken, surgical oncologist, leaders of the Stand Up to Cancer Melanoma Research Team, explained via email. “Even if you don’t get sunburned, UV exposure can still increase your risk of skin cancer.”
So how much SPF do we really need? How much sunscreen should we wear and how often should we reapply it? What is the difference between chemical and mineral sunscreens? We asked experts.
What does SPF mean?
The SPF or sun protection factor of a sunscreen indicates how much protection a product offers.
When sunscreen is developed in labs, the SPF rating is determined by how long a product protects against sunburn, explains Dr. Arash Akhavan, a board-certified dermatologist and owner of The Dermatology and Laser Group in New York City. This means that if untreated skin usually takes 10 minutes to burn, skin treated with SPF 30 would take 30 times longer to burn.
But that’s not how it works in practice, experts say. According to the US Food and Drug Administration, “SPF is not directly related to the time of sun exposure, but to the amount of sun exposure”. The amount of sun exposure depends on the time of day. For example, sun exposure will be greater in the afternoon than in the early morning. It also depends on geographic location: for example, places closer to the equator get greater sun exposure than places closer to the poles.
Other factors that influence the level of protection a sunscreen provides are the person’s skin type and how often and how thoroughly he/she reapplies it.
What is the difference between SPF 30 and SPF 50?
SPF levels are determined by the percentage of UVB rays they block, Rogers explains. SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97% and SPF 50 blocks 98%. SPF 100 blocks 99% of UVB rays. A sunscreen with SPF 50 therefore blocks more UVB rays and therefore offers greater protection against the sun than a sunscreen with SPF 30.
Does it matter what level of SPF I use?
As a general rule, you can’t overdo it with sunscreen.
“I would recommend using the highest SPF rating you are comfortable with,” says Akhavan.
Both AAD and that of Great Britain National Health Service (NHS) recommends using a minimum SPF level of 30.
In addition to providing better sun protection, higher SPF levels help compensate for human error, Rogers says. Many people use much less than the recommended amount of sunscreen for each application, reducing the level of protection. For example, if you apply SPF 30 too lightly, you may only get the coverage of SPF 15.
“We want the number to be high enough so that even if you use less than the recommended amount, you still get significant protection,” says Rogers.
What is the difference between UVA and UVB rays?
While SPF refers to the percentage of UVB rays that a sunscreen blocks, UVA rays can also damage our skin. According to the The University of Texas MD Anderson Cancer Center, “UVA radiation is responsible for 95% of all UV rays that reach the Earth.” These rays penetrate deep into our skin and result in a tan. They also damage collagen and cause wrinkles.
UVB rays do not penetrate deeply into the skin, but are very powerful. The damage they cause can lead to skin cancer and cataracts.
To protect oneself from both UVB and UVA rays, the FDA recommends its use broad spectrum sunscreens, which protect against both.
What is the difference between physical/mineral and chemical sunscreen?
Physical or mineral sunscreens and chemical sunscreens work on different levels of the skin.
Chemical sunscreens contain sun-protective ingredients that are absorbed into the skin, says Akhavan. These generally include ingredients such as avobenzone, homosalate, octisalate and octocrylene. These ingredients “absorb the UV rays and undergo a chemical reaction that removes the harmful energy from the UV rays before it can damage skin cells,” Akhavan explains.
Physical sunscreens, also called mineral sunscreens or sunblocks, usually contain zinc oxide and/or titanium oxide. These minerals are located on the top layer of the skin and reflect the sun’s rays, preventing them from penetrating the skin. Mineral sunscreens are often recommended for people with sensitive skin, says the AAD.
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Do my face and body need different SPF levels?
There’s no reason to use different levels of SPF on your face and body. SPF 30 is the minimum recommended level for both, says Akhavan.
But the best sunscreen is one that you will use consistently, and different types may be necessary in different situations. “I recommend using several different sunscreens,” says Rogers. She calls these your “sunscreen staples.”
An everyday facial sunscreen — one you wear to work and under makeup — may be tinted and less water-resistant, because water-resistant sunscreens are “less cosmetically elegant,” says Rogers. A heavier and more water resistant formulation would be better suited for outdoor and water use.
“There is no one sunscreen that will make you happy in all those different situations,” she explains.
Who should wear sunscreen?
In principle, everyone over the age of six months should wear sunscreen. This applies to babies under six months of age AAD recommends keeping the use of sunscreen to a minimum – protect them from the sun by keeping them in the shade and wearing sun protective clothing instead.
For everyone else, SPF 30 or higher is standard. Rogers notes that darker-skinned people have more innate sun protection and therefore take longer to tan or burn – but they are also susceptible to skin cancer.
“People of all skin colors are at risk for skin cancer, skin aging and sunburn when they spend time in the sun,” the FDA said. is reading.
How much sunscreen should I use?
Probably more than you think.
For each application, Block and Hieken recommend about 1.5 ounces (about one shot glass) of sunscreen on your body, and half a teaspoon total for your face and neck.
For spray sunscreens, they say to apply “until an even glow appears on the skin.”
How often should I reapply sunscreen?
Experts say you should completely reapply the sunscreen (the entire shot glass and half a teaspoon) at least every two hours. FDA guidelines recommend additional applications “if you swim or sweat.”
Not reapplying is where many people fall short in their sun protection, says Rogers. “Sunscreen only works as well as your application.”
Are there alternatives to sunscreen?
Although sunscreen is an important part of sun protection, experts agree that the best way to avoid harmful ultraviolet rays is to stay out of the sun when possible.
Block and Hieken suggest avoiding the outdoors in the middle of the day, when the sun’s rays are strongest: “Bring it indoors between 10 a.m. and 4 p.m.”
Rogers also recommends sun protective clothing, which she says can be more effective than sunscreen because there is less room for human error. “You don’t have to buy expensive UPF clothing either,” she says, referring to the ultraviolet protection factor, a measure of how much protection a garment provides against UVA and UVB rays.
Dark-colored clothing provides significant sun protection, says Rogers. White clothes, she warns, don’t offer nearly as much.
“A white cotton T-shirt gives you a UPF of nine,” she explains. “A gray cotton T-shirt gives you a UPF of 98.” There are no formal UPF requirements for clothing, but the Skin Cancer Foundation says that clothing with a UPF of 30 to 49 provides “very good protection,” and that clothing with a UPF of 50 or higher is rated “excellent.”
Ultimately, the best sun protection is a combination of all these tools. “Everyone has a different relationship with the sun,” says Rogers.