Research carried out by the CNRS research institute and scientists from the Louvre Museum indicate that the heavy eye make-up used by ancient Egyptians such as Cleopatra may have helped to fight off bacteria which can cause eye infections.
The make-up used could take up to a month to formulate as the chemicals did not occur naturally, the black and green powders which were applied thickly around the eyes contained doses of lead salts, which at low levels produce nitric oxide. Research found that these small amounts of lead could actually have a positive effect which would boost the bodies immune system making them less susceptible to bacterial infections such as conjunctivitis. Ancient Egyptian manuscripts suggest this make-up would have a magical effect on the wearer which would protect them against several illnesses.
According to the study published in the Journal of Analytical Chemistry a microscopic electrode 1/10th the thickness of a human hair was used on a single cell to measure the effect of the lead chloride. Raised levels of physiological activity was discovered related with immunity, it has been suggested that these lead compounds may have been deliberately fabricated to prevent and treat eye infections by encouraging the action of the immune cells.
I think its fair to say we definitely do not encourage the use of lead based substances today, it would certainly not get by the health and safety nannies. Just recently Mintel had warned that out of date cosmetics such as mascaras and eye pencils are a perfect breeding ground for germs and bacteria, consequently you should always take note of the use by date on such items to avoid infections.
The research is detailed here from the Journal of Analytical Chemistry on 15th January 2010.