Young Indian Girl With Pigtail And The Red Bandanna

Soldiers wear them to keep their own sweat and blood out of their eyes.
Kitchen staff may wear them to keep hair from falling into the food that they prepare.
Bandanas are also traditionally used as handkerchiefs by manual laborers and outdoorsmen, since they more practically hide stains than a white handkerchief. Thus they come to symbolize social revolutions. Anarchists participating in a black bloc, as well as other protestors, may wear a bandana over their face to conceal their identity and provide some protection against tear gas and pepper spray.