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I heard that mineral sunscreens are less toxic than chemical ones, but they often go on white. Some with nanoparticles seem to go on clearer—but are they safe?
Mineral sunscreens, whether made with microscopic nanoparticles or not, tend to be a better choice than sunscreens containing chemicals like oxybenzone, which is linked to hormone disruption and skin allergies. It’s true that mineral sunscreens with zinc oxide and titanium dioxide can go on white, so some sunscreen manufacturers have decreased the mineral-particle sizes, often to nanoparticles, which helps prevent “lifeguard nose.”
There is concern that tiny nanoparticles could cross the skin barrier and enter cells after application, or they could pass into the bloodstream after inhalation and cause organ damage or cancer. So far, many studies show that nanoparticles in sunscreens do not penetrate unbroken skin. But these nanoparticles will almost certainly get into the bloodstream if applied over broken skin, like an abrasion or open wound. To be safe, apply mineral sunscreens only to unbroken skin, and choose a lotion, rather than a spray, to avoid inhalation.