What are the black bars beneath American Footballer's eyes are

I often see football players with black bars right under their eyes. I can't figure out a reason why they are necessary. What are they used for?

Hughie Gallacher: the free-scoring Newcastle and Chelsea forward who became football's original bad boy

Pelé dies aged 82: tributes paid to a football great, Pelé

Rotherham blue plaque for first black footballer - BBC News

What are the black bars beneath American Footballer's eyes are used for? - Sports Stack Exchange

2022 NFL Free Agent Rankings: Top 200 players expected to enter free agency, NFL News, Rankings and Statistics

Footballers' Lives with Matthew Snoddy: A gambling addiction nearly killed me but God saved my life and I owe Him everything, now I want to help other people on a similar journey

Todd Marinovich Bio - Drug Problems of QB Todd Marinovich

Frontiers Cerebral blood flow regulation is not acutely altered after a typical number of headers in women footballers

The Essential Stories: 'The band is on the field!' - The greatest play in college history - Eurosport

Eye black - Wikipedia

Why do football players wear black paint under their eyes? - Quora

8 Best Base Layers for for Running and Strength Training in 2024