While Skittles don't include white in their line-up, Dr. Johnson-Arbor theorizes that titanium dioxide is used to help contain all the other beautiful colors.

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 Lithopone B301, Lithopone B311 powder itself may vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant might be used, like 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.

A European ban of titanium dioxide in food took effect in 2022, but it is still legal for use in food in the U.S.

Prof Matthew Wright, both a member of the FAF Panel and chair of EFSA’s working group on E 171, said: “Although the evidence for general toxic effects was not conclusive, on the basis of the new data and strengthened methods we could not rule out a concern for genotoxicity and consequently we could not establish a safe level for daily intake of the food additive.”