Although barium sulfate is almost completely inert, zinc sulfide degrades upon exposure to UV light, leading to darkening of the pigment. The severity of this UV reaction is dependent on a combination of two factors; how much zinc sulfide makes up the pigments formulation, and its total accumulated UV exposure. Depending on these factors the pigment itself can vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant may be used, such as a small amount of cobalt salts, which would be added to the formulation. This process creates cobalt-doped zinc sulfide. The cobalt salts help to stabilize zinc sulfide so it will not have as severe a reaction to UV exposure.
Titanium dioxide helps protect the skin from both UVA and UVB rays. Plus, it’s generally considered to be safe for sensitive skin types. Not only that, but it might also make for sunscreens that are more suitable for children and infants since it’s much less likely to cause stinging compared to chemical sunscreens. And when used in foundations, titanium dioxide can even provide a little extra sun protection on top of your daily SPF.
