If you've ever wondered, "How does sunscreen even work?" you're not alone. We asked clean cosmetic chemist Krupa Koestline and board-certified dermatologist Rebecca Marcus, M.D., to explain.
"UV rays signal the skin to increase transcription of the tyrosinase gene," Koestline said. Tyrosinase is responsible for the first step in melanin production.
"Sunscreen works by reducing and limiting the signal to reduce tyrosinase production," she explained. Translation: Sunscreen increases the amount of UV radiation needed to create sun damage on the skin.
However, there is a difference between the mechanisms behind mineral and chemical formulas. "Chemical sunscreens work by absorbing UV radiation and catalyzing a chemical reaction that transforms these rays into heat, which is then released from the skin," Marcus explained.
On the flip side, mineral sunscreens create a sun-blocking barrier. "Physical sunscreens physically block UV radiation from reaching the skin by deflecting UV rays," she continued.
At the moment, zinc oxide and titanium dioxide (common ingredients in mineral SPF) are the only two ingredients the Environmental Working Group has deemed safe for use and effective at protecting the skin from UV damage.
If you want to learn more, we've covered the difference between mineral and chemical sunscreen before.