From The Secret Lives of Color by Kassia St. Clair.
Lurking in the Egyptology section of the Louvre in Paris is a curious object. It is a squat, sparkling white statuette of a bowlegged creature, whose red tongue lolls from a mouth lined with sharp teeth; it has pendulous, triangular breasts; a fierce blue V for eyebrows; and a long shaft of a tail that dangles rudely between its legs. Made between 1400 and 1300 B.C., it depicts the god Bes, who, while he may look terrifying, was actually rather sweet: a fearsome fighter, he was popular with ordinary Egyptians because he was a protector, particularly of homes, women, and children. What he was protecting in this case, though, was rather different: hidden in the statuette's hollow head is a small container intended for kohl eyeliner. ...
In 2010, French researchers analyzing the traces of powder found in kohl pots discovered that they also contained something even more precious: man -made chemicals, including two kinds of lead chlorides that would have taken around a month to brew. Mystified, they conducted further tests. To their astonishment, these chemicals were found to stimulate the skin around the eye to produce around 240 percent more nitric oxide than usual, significantly reducing the risk of eye infections. In a time before - antibiotics, such simple infections could easily lead to cataracts or blindness. Kohl, like the little pot in the shape of the fearsome Bes, was a very practical form of protection.