Until relatively recently on the grand historical scale, lead was a common makeup ingredient, used in eyeliner and as powder because of its lovely pigment and versatility. Unfortunately, lead also poisons blood, leads to facial deterioration and—oh yeah—kills people. But now, scientists studying ancient Egyptian cosmetics say that our ancestors might not have been so crazy after all. Even though lead is harmful, it may have had a much more immediate benefit for its users: preventing infections. During the Nile's flood stage, it was common for people to get eye infections, yet lead-based liners could have killed the bacteria before it entered the eye. Very handy. I'll be honest, it's not something I'm going to road-test personally for you—again, not keen to try death by lead poisoning—but it's food for thought on a Thursday morning.