Sideburns can be worn and grown in combination with other styles of facial hair, such as the moustache or goatee, but once they extend from ear to ear via the chin they cease to be sideburns and become a beard, chinstrap beard, or chin curtain.
Following the eighteenth century, when European men west of Poland were universally clean-shaven, sideburns, like beards, began to grow in popularity during the Napoleonic period. The trend eventually made its way to Meiji Japan, in the first wave of Western fashion there. The return of facial hair in Western Europe began as a military fashion, at first inspired by the heroic sideburns sported by hussar regiments.
Nineteenth century sideburns were often far more extravagant than those seen today, similar to what are now called mutton chops. As with beards, sideburns went quickly out of fashion in the early twentieth century, and in the First World War in order to secure a seal on a gas mask, men had to be clean-shaven; this did not affect mustaches.
Sideburns gained new connotations in 1960s hippie subculture: the struggle of a New Jersey youth to wear sideburns to his public high school graduation made a newspaper article in 1967 and in the 1970s among youth subcultures such as hippies and skinheads. Sideburns also became a symbol of the gay club scenes of San Francisco and Sydney, primarily Lambchops.