No, this isn’t a new SPF mechanism—physical sunscreen is just another way to say mineral sunscreen.
The descriptor makes sense, as mineral sunscreens manually block UV rays by creating a barrier on the skin (sort of like a physical shield). Think of them like a reflecting pane of glass: Some of the rays hit the SPF filters and bounce off, shielding the skin below from damage.
Chemical sunscreens, on the other hand, work by absorbing the UV rays and triggering a chemical reaction, which then transforms the UV into heat.
But as author and chemist George Zaidan previously told mbg, mineral sunscreens also do some absorbing—just like their chemical counterparts. Essentially, they work in two ways: First by blocking some rays, and second by absorbing the rays and deflecting their damage by turning it into heat.
At the moment, zinc oxide and titanium dioxide (both mineral, or physical, sunscreens) are the only two ingredients the Environmental Working Group has deemed safe for use and effective at protecting the skin from UV damage.
As long as the minerals are non-nano (read: aren’t broken down into smaller bits), they are deemed safe for oceans, as research shows they don’t cause coral bleaching or affect marine life—another worthy perk.
However, mineral sunscreens have been known to leave a hefty white cast. That being said, there are plenty of sunscreen formulas on the market today with mineral ingredients as well as tints and oils to minimize a chalky appearance—here’s a list of our current favorites if you’re ready to stock up.