You’ve Got SPF Questions, We’ve Got Answers (From a Dermatologist)

Last Update: March 21, 2024

Remember the days when sunscreen was a product you’d only use before a day at the pool or a particularly hot beach vacation? You’d slip a bottle of something coconut-scented out of your beach bag, absentmindedly smear it across your nose and over your shoulders, and think you were covered for a whole day of hopping in and out of the water. 

Chances are, you’ve learned a thing or two about proper SPF use since those days. You now know that you need to wear sunscreen every day—not just before a day in the sun—and that in fact, it’s one of the most important parts of your entire skincare routine. To prevent skin damage (and even skin cancer), SPF should be non-negotiable. But even if you consider yourself a skincare aficionado thanks to the wealth of Reddit forums and Tik Tok tutorials available, SPF remains one of the more complex and misunderstood skincare concepts.

You’ve got burning SPF questions—but lucky for your skin, we’ve got answers. 

What is SPF? 

SPF stands for “sun protection factor.” The SPF number refers to how much UV radiation would be required to burn skin protected by sunscreen in relation to skin without sunscreen. The SPF refers to the amount of solar exposure that the skin can withstand, not necessarily the amount of time a person can spend in the sun. 

How do I choose an SPF number? 

While it may seem like a no-brainer to simply reach for the sunscreen with the highest SPF to achieve the best protection, the SPF scale is not linear, so at a certain point the difference in effectiveness between SPF levels begins to decrease, making the higher levels fairly similar in terms of performance. “I recommend a minimum of SPF 30 for daily use on exposed skin and SPF 50 or more for outdoor activities,” advises Dr. Brooke Grant Jeffy, MD, an Austin-based dermatologist.

How much sunscreen should I use? 

The general idea is this: the higher the SPF level, the more protected your skin is from the sun. However, things like proper application, amount of sunscreen used, and reapplication all affect the effectiveness of your SPF products. “It is generally accepted that we actually only get about half the protection we think we’re getting because we do not apply generously enough,” explains Jeffy. “To try to combat this, I recommend patients be generous with application and apply two coats.” The American Academy of Dermatology recommends that adults use enough sunscreen to fill a shot glass for their entire body; for the face, that’s about ½ teaspoon full.

What is the difference between chemical sunscreen and physical sunscreen? 

When choosing the right sunscreen, you’ll first have to choose between chemical sunscreens and physical sunscreens. Physical sunscreens work by creating a physical barrier between your skin and the sun, using minerals to actually deflect UV rays away from the skin. Chemical sunscreens use synthetic compounds to convert UV rays into heat and release them from the skin. 

Here’s how the two stack up:

Physical sunscreens: 

  • Sit on top of skin
  • Block sun with minerals like zinc or titanium dioxide
  • Heavier and thicker
  • Also called “natural sunscreen” or “mineral sunscreen”

Chemical sunscreens: 

  • Absorb into skin
  • Use chemical compounds that convert UV rays into heat
  • Thinner texture and more lightweight 
  • May contain chemicals linked to health problems and coral reef damage (though more natural brands avoid these ingredients)

Which facial sunscreens won’t make my face break out? 

Breakouts are a major concern for many when choosing a sunscreen, but according to Jeffy, there’s a simple solution: a non-comedogenic sunscreen that won’t clog pores. She adds, “There are sunscreen products that have added ingredients to help calm acne, such as niacinamide or lactic acid. Powder-based mineral sunscreens also tend to be well-tolerated by those with acne-prone skin.”

Does sunscreen pollute the ocean? 

Unfortunately, yes—in some cases. Many common types of sunscreens contain chemicals that are deadly to coral reefs; when humans wear these sunscreens and swim in oceans, the sunscreen washes off their skin and disrupts the essential relationship between coral and algae. In 2018, Hawaii even banned the use of sunscreens containing chemicals like oxybenzone and octinoxate that harm coral. To avoid sunscreens that destroy coral reefs, it’s best to choose “reef-safe” mineral sunscreens formulated without these harmful chemicals

What is a broad spectrum sunscreen?

Broad spectrum sunscreens are sunscreens that protect against each of the two types of UV rays. According to Jeffy, many SPF products protect the wearer against the UVB rays that cause the skin to burn; however, they may not protect against UVA rays, which are the rays that cause your skin to tan but also cause wrinkles and other signs of skin aging. “You want a product that says it is ‘broad spectrum’ so that it protects against both UVA and UVB rays,” explains Jeffy.

Do I need a different sunscreen for my face and body? 

This one is all about personal preference. “There are certainly sunscreens that feel lighter and look more cosmetically elegant that may be preferred on the face,” Jeffy explains, but she’s quick to say that you can easily use the same sunscreen for your face and body. If you’re concerned about acne breakouts on the face, it’s always smart to choose a non-comedogenic sunscreen.

How often do I need to reapply sunscreen?

Properly applying—and reapplying—sunscreen is perhaps the most important step in protecting your skin against the harmful effects of the sun. Jeffy recommends reapplying sunscreen every one to two hours, unless you’re swimming or excessively sweating. If you notice your sunscreen wearing off due to water or sweat, it’s always best to reapply more frequently. 

Are chemical sunscreens bad for your health? 

Some of the chemicals that are most effective in protecting your skin against UV damage may also have adverse effects on your health. Animal studies suggest that chemicals like oxybenzone may interfere with hormones such as estrogen, and human studies show traces of oxybenzone in human blood and breast milk. The FDA is currently studying the safety of 12 chemicals commonly found in sunscreens, including oxybenzone, avobenzone, homosalate, octinoxate, octisalate and octocrylene. If you want to avoid these chemicals, stick with mineral sunscreens instead of chemical sunscreens. 

Does sunscreen go bad? 

Yes—so let this be your reminder to check your medicine cabinet and toss any expired SPF products. The FDA requires sunscreens to remain at their original strength for at least three years, but after that time window, you should assume that your sunscreen is no longer effective. 

How can I make my sunscreen more effective? 

No matter which sunscreen you choose, you can always take a few other precautionary steps to prevent sun damage. Wearing long-sleeved clothing adds a layer of physical protection from the sun, and it’s always smart to wear a hat and sunglasses with UV protection to shield your eyes and face. Seek shade when you know you’ll be outside in direct sunlight, and try to head indoors during the sunniest parts of the day (between approximately 1 p.m. and 3 p.m.) For particularly sun-heavy days, you may even want to invest in sun-protective clothing with a UPF (Ultraviolet Protection Factor) of 30 or higher. 

Sunscreens at Thrive Market

Which sunscreen is right for you? Below are a few of our sunscreens for all ages, skin types, and lifestyles. 

For face and body: Thrive Market Broad Spectrum Mineral Sunscreen SPF 30

For anti-aging: ACURE Radically Rejuvenating SPF 30 Day Cream

For lips: Badger SPF 15 Lip Balm

For SPF makeup: MyChelle Sun Shield Liquid Tint SPF 50

For easy application: Babo Botanicals SPF 30 Sheer Zinc Continuous Spray Sunscreen

For sports: THINK Sunscreen SPF 50+

For babies: THINK Safe Sunscreen SPF 50+

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Amy Roberts

Amy Roberts is Thrive Market's Senior Editorial Writer. She is based in Los Angeles via Pittsburgh, PA.

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