By now, you know the skin-health drill: Wear sunscreen. Reapply it. Daily. No exceptions. But do you know the differences between the oft-used terms physical and chemical when it comes to the non-negotiable product? The experts break it down.
They each protect differently:
The American Academy for Dermatology (AAD) summarizes this one succinctly in an easy-to-understand sentence: “A physical sunscreen protects by deflecting the sun’s rays, while a chemical one absorbs the sun’s rays.”
They each have different ingredients:
Physical sunscreens typically contain zinc oxide and mineral oxide, says Montclair, NJ dermatologist Jeanine Downie, MD. “These are physical blockers from the sun that reflect the sun’s rays,” she explains, adding that they tend to be whitish and can be difficult to rub into darker skin tones. “Chemical sunscreens also protect against UVA and UVB and can protect against infrared and HEV light as well. The active ingredients in chemical sunscreens may include avobenzone, octinoxate and oxybenzone.”
But some cross over…
Not to get overly complicated with formulation facts, but the AAD does point out that the distinction between the duo isn’t always so black and white when it comes to ingredients: “Some sunscreens use both types of active ingredients, so they contain one or more active ingredient found in physical sunscreen and chemical sunscreen,” the Academy notes and offers this tip for how to tell: “You’ll find the list of active ingredients that a sunscreen contains on the container under the heading ‘active ingredients.’ If you are concerned about certain sunscreen ingredients, look for a sunscreen that contains different active ingredients.”
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They offer different advantages:
According to Dr. Downie—who stresses that everyone should use an SPF 30 every single day rain or shine regardless of your ethnicity, and it must be reapplied every two hours—chemical SPF varieties are “really good for if you need something that is more water-resistant or if you are going swimming. They tend to rub better into brown and black complexion.” On the other hand, when it comes to physical sunscreens, she lists that “advantages include that they tend to be less irritating and more hypoallergenic, but they can be thicker and might feel heavier on the skin.”
And different aesthetic treatments call for different options…
As Lydia Sarfati, CEO and founder of Repêchage explains, when it comes to post-facial or post any invasive procedure—laser hair removal, microneedling dermaplaning and waxing—you need to protect skin from UV light and environmental aggressors like free radicals and pollution with mineral-based, physical sunscreens, such as zinc oxide and titanium dioxide. “These ingredients work by creating a full-spectrum, physical barrier to protect the skin,” she says. “This type of protection is crucial after professional treatments. A long-lasting physical barrier in a waterless formula that combines mineral zinc oxide with ingredients that are high in natural antioxidants such as seaweed is ideal post-facials. I recommend non-migrating formulas that will not seep into the eyes causing redness and irritation; I also recommend mineral-based foundation to be applied after facial treatments, to help boost the physical protective layer.”
In both cases, number doesn’t necessarily matter:
While the AAD does recommend using a sunscreen with an SPF of at least 30, Sarfati warns that, after that, a higher SPF doesn’t tell the whole story. “Many people assume that a chemical sunscreen provides better sun protection because it may have a very high SPF. There are many factors involved when choosing a correct sunscreen. Full spectrum protection, which includes UVA and UVB light is crucial to prevent damage that can lead to skin cancer and skin aging. Physical sunscreens are naturally full-spectrum, while chemical sunscreens may not block UVA and UVB equally. The important point to know is that the higher numbers of SPF doesn’t give you more protection; they give you more extended protection. SPF, which stands for Sun Protection Factor, indicates how long you can stay exposed to the sun before you have to reapply your sunscreen.”
The bottom line:
Chemical sunscreens: Allow UV light into the skin. “Once the light is absorbed, the chemicals in the sunscreen create a chemical reaction in which UV light is converted to heat, and the heat dissipates,” Sarfati says. “This can create even more sensitization on skin that has been aggressed by treatments such as dermaplaning or extensive extractions.”
Physical sunscreens: Create a physical barrier on the surface layer of the skin, preventing UV light and pollution from affecting the upper skin layers. “This effectively creates a protective shield from causing any sensitization from the UV light,” explains Sarfati. “The cons of zinc and titanium dioxide have been that, in the past, they created an opaque, white cast to the skin. This has now been greatly reduced with micronized formulas.
