The pros don’t think green beer is a festive St. Patrick’s Day tradition. To them, green beer is green—inexperienced, the same way somebody new on the job is green. Serious Eats describes the problem : green beer hasn’t lost its acetaldehyde, which ruins a beer’s taste if there’s too much. Brewers who serve beer before it’s fully fermented end up making green beer that tastes bad.

In the early 1900s, that was a huge problem. Or at least advertisers wanted consumers to think it was.

A well-advertised epidemic of biliousness

Biliousness sounds like bile, and that’s because it refers to excess bile or gastric distress. Biliousness was the primary claim of beer-makers who wanted to stop green beer from hitting the shelves. As early as 1899, Wieland’s Extra Pale jumped on the “green beer” train, warning consumers that “Green beer is fermented in a high temperature, and put on the market before fermentation is complete. It may cause biliousness.”

Other beer-makers soon followed, the biggest being Schlitz. Using the gripping slogan “Schlitz Is Old Beer,” Schlitz insisted their beer would never “ferment in your stomach.” That was the backbone of a long-running national marketing campaign that promoted Schlitz’s age and refined techniques. But green beer was always the main scare tactic.

Was green beer really a problem?

“Green beer is extremely bad on the stomach and the nerves.”It’s tough to know how common biliousness was (people don’t report it to the police or their local paper). However, it wasn’t just Schlitz pushing the “green beer” scare. In addition to Wieland’s, in 1906, Budweiser joined the calls against green beer, as did other smaller breweries. In 1922, the Washington Times managed to track down a chemist who said, “green beer is extremely bad on the stomach and the nerves.” But by that time, green beer was already being redefined as a St. Patrick’s Day tradition.

Green beer becomes synonymous with…food coloring

All it takes to make green beer is a little blue food coloring (which mixes with the yellow hue of the beer). As early as 1910, bartenders were experimenting with special St. Patty’s day treats. In 1910, the Spokane Press proclaimed, “Green Beer Be Jabbers!” in an excited headline (yes, that was the actual headline). As the writer poetically put it, “It tastes like beer and looks like paint, or rather like the deep green waves in mid-ocean with the sun striking them through.”

Experiments around the country followed, and by 1912, inspectors were looking askew at green beer in New York City. Green beer had begun the gradual transition from overeager brewers to overeager drinkers. Though brewmasters still call beers “green,” most people will drink it on St. Patrick’s Day (though it helps if they’ve had a few already). Be warned: your biliousness may vary.