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Sunscreen Guide: Everything You Need to Know About SPF

It’s time to gear up for getaways, beach days, and bbqs which means summer responsibly—protect your skin. Here’s how to shop for SPF, the difference between physical and chemical sunscreens, why broad spectrum matters, and everything under the sun. 

Woman sunbathing by a pool

What is the difference between chemical and physical sunscreens?

The main difference between these sunscreens is the active ingredients they contain. If the active ingredient in your sunscreen is titanium dioxide, zinc oxide (or both), you have a physical sunscreen, more commonly known as mineral sunscreen. If your sunscreen doesn’t contain titanium dioxide or zinc oxide, you have a chemical sunscreen.¹

Some sunscreens are called hybrids because they contain one or more active ingredients found in chemical and physical sunscreens. To see what active ingredients your sunscreen has, look at the section on the container labeled “Active Ingredients.”²

Whether you have a chemical, physical, or hybrid sunscreen, they all form a protective layer on your skin that absorbs the sun’s rays. However, another key difference between these types of sunscreens lies in how they block rays. Physical sunscreens sit on the surface of your skin and act as a shield, while chemical sunscreens sink into your skin and act more like a sponge.³

Woman applying an SPF to her arm for sun protection

In addition to absorbing the sun’s rays, physical sunscreens reflect the sun’s rays. Any of these sunscreens can effectively protect you from the sun if you select one that is broad spectrum, water resistant, and has an SPF 30 or higher.

And, of course, apply sunscreen daily, not just bikini days. “It’s important to wear sunscreen regularly,” says Hadley King, MD, a board-certified dermatologist based in New York City. “Much of the sun exposure and sun damage that we get is from daily incidental exposure, not just from days at the beach.”

What to look for when buying Sunscreen 

A few things to keep in mind before you slather and repeat.

SPF

The sun protection factor (SPF) measures how long the sunscreen will protect you from the sun’s UV rays. For example, SPF 50+ offers the highest protection, while SPF 30+ offers lower protection. Your level of sun exposure varies depending on your activities, the time of day, geographical location, and the UV index. If you frequently engage in outdoor activities for hours at a time or live in an area close to the equator, it’s best to choose an SPF 50 sunscreen to compensate for your level of sun exposure and adjust the frequency of reapplication.

Broad Spectrum

Broad spectrum sunscreens protect against both UVA and UVB rays. UVB rays cause sunburn and skin cancer, while UVA rays cause premature aging.

SPF values only indicate your sunscreen’s coverage against UVB rays, which is why it’s important to make sure your sunscreen is also labeled as broad spectrum. A broad spectrum sunscreen means it protects against both UVA and UVB rays, which have longer wavelengths and can penetrate deeper into the skin. UVB rays cause sunburn and skin cancer, while UVA rays cause premature aging.

Water Resistance

No sunscreen is truly waterproof, but they can be water-resistant. Experts recommend opting for water-resistant sunscreens, especially if you’re swimming or sweating from exercise or sports. According to the American Academy of Dermatology Association, sunscreens can only be water-resistant for either 40 or 80 minutes, so make sure to reapply them consistently afterward.

Ingredients

Aside from deciding between physical vs chemical sunscreen ingredients, avoid products that contain oxybenzone, which can disrupt hormonal balance and cause an allergic reaction. 

Skin Type

Additionally, consider your skin type, as fairer skin requires a higher SPF for protection. Sensitive or dry skin will require specific types of sunscreen. If you have dry skin, opt for creams and lotions to help your skin stay moisturized. Lightweight gels or powders with a matte finish are good for oily skin to help keep shine under control. Meanwhile, mineral, non-comedogenic, and hypoallergenic formulas are recommended for sensitive and acne-prone skin.

Different Types of SPF Products

The most popular forms of sunscreen (including their pros and cons) to help you determine which is best for you.

Sunscreen Creams and Lotions

While you might envision the traditional pasty white cream when you think of sunscreen, fortunately these formulas have gotten a serious upgrade over the years. Today there’s a variety of lightweight options that benefit all skin tones and concerns. 

Sunscreen creams and lotions are emulsions of oil and water, giving them an easy-to-spread texture that makes coverage pretty seamless—you’re less likely to miss spots during application. For context, an adequate amount is 2 milligrams (mg) per square centimeter, according to the U.S. Food and Drug Administration (FDA). (That translates to about 1 ounce [oz] of sunscreen, or a full shot glass, per the AAD.) Applying — and reapplying — this quantity will ensure you reap the sun protection factor (SPF) shown on the sunscreen bottle.  

The cons of creams and lotions? They’re more challenging to use on the scalp, and makeup wearers may find them hard to reapply, says Dr. King. Some formulas can also clog pores when used on the face; be sure to look for the word “noncomedogenic” (meaning it won’t clog pores) on the bottle before you add it to your shopping cart. 

Sunscreen Sprays

Spray sunscreens are a well-known alternative to lotions and creams for those who prefer a lighter-weight texture. Popular options in this category include aerosols, continuous spray nonaerosols, and pump tops, with options for the face and body.

But one of the most common mistakes people make with an aerosol spray is not rubbing it in, since many spray bottles don’t instruct users to do so. Don’t just spray and go, advises the AAD — rather, rub your spray sunscreen into your skin to ensure even coverage.

Another drawback, outlined in a Griffith University Study published in November 2021, is that applying spray sunscreen in windy conditions results in a significant loss of sunscreen. Researchers found that four of the five sunscreen products tested would need more than one bottle to provide enough full-body coverage in 20 kph (12 mph) wind conditions. (The solution: Consider applying your sunscreen indoors to ensure you’re not wasting product. Then, wait the AAD-recommended 15 minutes before heading to your outdoor plans.)⁵

Aerosol spray sunscreens may also contain ingredients (like ethyl chloride, propellants, and di- and tri-chlorofluoromethane) that can irritate sensitive skin, says Christina Chung, MD, a board-certified dermatologist with Schweiger Dermatology Group in New York City. Unfortunately, “there is no specific ingredient that consumers with sensitive skin should look for in a spray sunscreen,” she says. “Generally speaking, aloe, chamomile, and antioxidants can be soothing and have anti-inflammatory properties, but even they are not the holy grail for sensitive skin.” She recommends opting for a mineral sunscreen, which is less likely to irritate the skin than a chemical sunscreen — but, she adds, the process of finding a spray sunscreen that suits your skin “may take a little trial and error.” 

And finally, don’t spray directly onto your face, to avoid inhaling your SPF. Instead, spray your sunscreen of choice onto your hands and then rub it on your face.

Sunscreen Sticks

Multipurpose sunscreen sticks are another popular option for the face and lips and have come along way in terms of texture. Plus, thanks to their mess-free packaging, this form of sunscreen is ultra-portable and handy for travel.

Sunscreen sticks usually contain oil, no water, and a high wax content that gives them that solid shape, says Lu. While old-fashioned sticks get a bad reputation for clogging pores, there are many new noncomedogenic formulations on the market these days. 

They’re frequently used to protect the under-eye area, but they’re suitable for use all over your face.

One important thing to keep in mind, per Lu, is that it’s easy to underapply when it comes to stick formulations. The key to protecting yourself, per the AAD: Pass the sunscreen stick four times back and forth over the area you’re covering. Then, rub the sunscreen in to ensure an even layer of coverage. 

Sunscreen Powder 

Powder sunscreens are a portable, convenient option for reapplying sunscreen to the face and scalp. Their formulas contain the mineral sunscreens titanium dioxide and zinc oxide in powder form, say Fu and Lu. This makes them a smart reapplication choice for those with sensitive skin and makeup wearers who diligently reapply every two hours, as recommended by the AAD. Many of them even double as makeup-setting powders that reduce shine.

Powder sunscreen is a game changer for reapplication to the face and scalp. But in Dr. Chung’s words, it’s a “second line of defense” — and not an ideal option for a base layer, because a significant amount of powder is required to achieve full SPF protection, and most people only apply a light layer. In other words, it’s good for reapplication, but you should still use a nickel-size dollop of lotion on your face at the start of the day, as the Skin Cancer Foundation recommends

Similar to sunscreen sprays and unlike creams and lotions, one of the drawbacks with sunscreen powder is that you don’t have full control over the coverage area, and, as touched on above, it’s difficult to quantify how much you’ve applied to your skin to achieve the SPF factor on the bottle. Plus, it’s a costly and time-consuming option if you’re planning to apply it to your body.

Choose a Formula You’ll Use

As for their efficacy, Fu and Lu say they function similarly to lotion and cream formulas, and should be applied the same way: by rubbing a generous amount into the skin.

The bottom line, Chung says, is that “the best sunscreen is the sunscreen you will actually use.” But applying your formula of choice — be it a lotion, cream, gel, spray, or stick formula — is the bare minimum. To get the most out of your SPF and keep your skin safe, be sure to apply it to all areas exposed to UV rays, apply an adequate amount, and reapply every two hours.

Frequently asked questions about SPF

What does SPF stand for?

SPF stands for Sun Protection Factor, and it indicates how much protection a sunscreen provides. 

How much sunscreen should I apply?

Adults should apply about two tablespoons or one shot glass of sunscreen to cover all skin not covered by clothing. This includes the tops of your feet, neck, ears, and head.

How often should I reapply sunscreen?

Reapply sunscreen every 2-3 hours, or more often if you are swimming or sweating.

What SPF should I use?

The target range is from SPF 15 to 50, although a minimum of SPF 30 is commonly recommended. SPF 50 may be better for people with fairer skin, while people with skin cancer or other conditions affecting the skin should ask their doctors if an even higher SPF is needed.

Should I use sunscreen before going outdoors?

Apply sunscreen to dry skin 15 minutes before going outdoors.

 

 

Jessica Timmons. What’s the Difference Between Physical and Chemical Sunscreen? Healthline. February 2022.  Source
The American Academy of Dermatology Association. Update April 2024. Source
Cole C, Shyr T. Metal oxide sunscreens protect skin by absorption, not by reflection or scattering. Photodermatol Photoimmunol Photomed. January 2016. Source
Marisa Petrarca. Lotion, Spray, Powder, Stick, Gel: Which Sunscreen Is Right for You? Every Day Health. Source
Testing Aerosol Sunscreen Products: Exploring The Impact of Wind on the Application of Sunscreen. Compiled by Dr Elke Hacker Griffith University, Brisbane, Australia November 2021. Source