Our relationship with the sun is complicated: We need it, but that doesn't necessarily make it good for us either.
Everyone — regardless of complexion — is susceptible to its adverse effects, including sunburns, premature aging, hyperpigmentation and ultimately skin cancer.
That's why daily application of sunscreen is essential and is one of the most important ways we can limit our sun exposure. However, the type, strength (SPF) and application of sunscreen can make a big difference in whether you're adequately protected.
We spoke with Annie Christenson, a medical esthetician at Houston Methodist, to learn what to look for when buying a sunscreen and tips for ensuring you're getting the right sun protection as advertised on the bottle.
Is a higher SPF value better than a lower one?
Technically speaking, yes. SPF stands for sun protection factor and is a measure of a sunscreen's ability to protect you from getting a sunburn. The higher the SPF value, the more sun protection you're going to get.
However, according to Christenson, just because a sunscreen has a higher SPF value doesn't necessarily mean it's going to provide you with more protection for longer. Rather, SPF — as defined and regulated by the FDA — is not related to time of solar exposure but by the amount of solar exposure.
The sun's rays are strongest during midday hours — 15 minutes of sun at 1 p.m. may be the equivalent of an hour's worth of sunshine at 9 a.m. Therefore, while an SPF 50 sunscreen may offer more protection than SPF 30, that doesn't mean it's going to last you much longer before you ought to reapply — which, according to Christenson, is at least every two hours if you're outside and active.
Moreover, the relationship between SPF and UV absorption isn't linear: SPF 15 blocks 93 percent of the sun's rays, whereas SPF 30, 50 and 100 only block a few more percentage points at 97, 98 and 99 percent, respectively. No sunblock can protect against 100 percent of the sun's UV radiation.
As for sunscreens lower than SPF 15, because they don't provide enough protection, they're required by law to include a warning label that says the product cannot prevent skin cancer or early aging — only sunburns.
"SPF 15 isn't enough for a number of reasons," says Christenson. "You should always have a minimum SPF of 30. You can find higher SPFs now, which may allow you to go a bit longer in between reapplying, but you're not going to get eight hours' worth of protection from any sunscreen."
What all to look for in a sunscreen
The American Academy of Dermatology recommends sunscreens that are:
- SPF 30 or higher
- Broad spectrum
- Water resistant
Broad spectrum refers to a sunscreen's ability to protect against both types of ultraviolet (UV) rays the sun emits. Ninety-five percent of the UV radiation that reaches the earth's surface is in the form of UVA, weaker rays that don't necessarily cause sunburns but contribute to premature aging and hyperpigmentation associated with prolonged exposure. UVB rays, however, are much more powerful, the primary cause of sunburns, inflammation and ultimately the DNA damage that leads to skin cancer.
While most sunscreens are broad spectrum, it's important you look for indicators on the label, since not all sunscreens protect against both types of UV radiation.
All mineral sunscreens — meaning those that contain zinc oxide or titanium dioxide as active ingredients — are considered broad spectrum, Christenson says. Most chemical sunscreens — which involve organic compounds that neutralize UV rays — are broad spectrum too, she says, but they either must say broad spectrum on the bottle or list avobenzone as an active ingredient. It's the only chemical filter approved to protect against UVA rays.
(Related: Mineral vs. Chemical Sunscreen: Which is Better?)
Common sunscreen mistakes and how to avoid them
Most people don't apply sunscreen correctly, which can reduce its SPF value and increase your risk of exposure. Christenson shares the most common pitfalls and how to correct them to ensure you're getting the protection you need.
1. Applying too little or incorrectly
They say an ounce of prevention is worth a pound of cure — in the case of sunscreen, that couldn't be more literal. One ounce — the size of a shot glass — is the amount of lotion necessary for an average adult to achieve the full SPF value as labeled on the bottle for their entire body.
However, most people don't apply that much, which can reduce how well the sunscreen actually protects your skin. That's why Christenson says, "there's no such thing as 'too much' sunscreen."
Sunscreen sprays are another reason why people don't get enough protection, says Christenson.
"A spray can be easier to use, but you have to apply enough, and you have to rub it in before it dries," she says. "I've had more people tell me that they've had serious sunburns because they chose to use a spray sunscreen over a lotion, so I recommend spray as more of an easy form of reapplication rather than the first layer."
It's also a common misconception that people with darker skin tones don't need as much sunscreen or any sunscreen at all. The melanin in deep skin tones only provides enough protection equivalent to about SPF 15. Remember, according to the FDA, anything less than SPF 15 is not enough to prevent sun-related damage, including aging, hyperpigmentation and skin cancer.
To ensure you're getting enough sunscreen, you can either double the application or adopt the "teaspoon rule" — an easy-to-remember guide for evenly applying sunscreen. Judging by eye, apply:
- 1 teaspoon to your face and neck
- 1 teaspoon on each arm
- 2 teaspoons to your front and back torso
- 2 teaspoons for each leg
2. Not reapplying as directed
As Christenson mentions, no sunscreen is going to be able to provide you with all-day protection from the sun. Most sunscreens start to lose their potency after two hours, in which case you'll want to reapply — but there are exceptions to this guideline, says Christenson.
"Being indoors, you don't really have to reapply," she says. "You're not sweating it off, you're not toweling it off after swimming. If you're sitting in front of your computer, and you're not close to any windows, you don't really have to reapply until you intend on leaving your office or home."
On the other hand, you might need to reapply every hour — if not sooner — if you're swimming, sweating or moving, according to Christenson.
A lot of sunscreens are water resistant, which means you can get wet and it's going to stay on. But Christenson notes that if the product doesn't say it is water resistant, then it's going to come right off, and you're exposed.
"Anytime you go in the water, if you get out of the water and towel dry, you need to reapply non-water resistant sunscreen because you either washed it off, sweated it off or wiped it off," says Christenson.
In fact, the FDA no longer allows sunscreen products to be labeled as "sweat proof" or "waterproof." Sunscreens can only be labeled as "water resistant" if they maintain their SPF after 40 minutes of swimming or sweating or "very water resistant" after 80 minutes — after which you'll need to reapply.
(Related: How Often Should You Reapply Sunscreen?)
3. Using expired sunscreen
The FDA requires all sunscreens to remain stable for at least three years. However, not all sunscreens have an expiration date, and, yes, prolonged exposure to heat and light can decrease the shelf life of the product.
The solution? Christenson says if people use sunscreen the right way — meaning an ounce every two hours — there's little reason you should have leftover sunscreen after a year.
"Don't baby your sunscreen," she says. "Not only do sunscreens expire, but you also really can't overuse sunscreen, which is why people should really use it up and invest in a fresh tube every year."
If you can't remember, it's best to throw it out and start fresh.
(Related: Does Sunscreen Really Expire?)
4. Relying solely on sunscreen
Sunscreen is but one tool in your arsenal to limit your sun exposure. Besides staying out of the sun when its rays are most intense, another method of protecting your skin involves wearing sun-safe clothing.
"Especially for people who have lighter skin tones and little kids that are going to be out in the pool all day long, I recommend sunscreen clothing," says Christenson. "You still want to wear sunscreen, but I also wear long sleeves when I'm at the pool."
Densely woven, dark or brightly colored clothing are considered more effective clothing options when it comes to sun protection, according to the Skin Cancer Foundation. Loose-knit, light and see-through fabrics such as linen are generally not recommended.
5. Applying only in sunny weather
"UVB rays, the ones that cause sunburns, penetrate straight through clouds," says Christenson. "You may not feel the heat of the sun, but a lot of people will say they've got their worst burn when it was cloudy out because they didn't apply any sunscreen."
Over 90 percent of UV rays can penetrate light clouds, according to the World Health Organization, and some clouds, such as cumulus clouds, can actually reflect and increase the amount of surface UV radiation. This is also true for water, snow and light-colored surfaces that reflect the sun's light.
