Eye black

One of the earliest known instances of a player wearing eye black is baseball legend Babe Ruth, who, in or around the 1930s, used the grease in an attempt to reduce sun glare.

The study concluded that eye black reduced glare of the sun and improved contrast sensitivity, whereas commercial anti-glare stickers and petroleum jelly (the control substance) were found to be ineffective.

[2] A study by Benjamin R. Powers at University of New Hampshire,[3] which improved on DeBroff's methodology, found eye black to reduce glare from the sun in women and in those whose eye-color was not blue.

This practice was banned on April 14, 2010, when the NCAA Playing Rules Oversight Panel (PROP) approved a proposal effecting "that players are not allowed to have any symbols or messages on their eye black starting in the 2010 season.

[9] In some birds, such as the peregrine falcon and the common kestrel,[10] it is possible to see black feathering underneath their eyes on their cheekbone, called a malar stripe.

This stripe has been evolved over time to serve the exact same purpose as it does in humans as described above, which is to reduce the glare from the sun into the bird's eyes, thus making it easier to spot prey.