Green beer is the delicious treat that many drink (and drink and drink) on Saint Patrick's Day. But the most colorful beer is not an Irish tradition: it's an American-born innovation that requires a lot of moxie and a little blue food coloring.

This is how it came to be one of our greatest traditions involving food coloring.

The origins of St. Patrick's Day's green beer

Regardless of who invented it, the first people to make green beer probably made it the same, slightly unintuitive way it's made today: a mixture of beer and blue food coloring (the blue mixes with the natural yellow of the beer to make green).

Generally, the drink is credited to Professor Thomas H. Curtin, a physician who made green beer for his clubhouse in New York. Curtin's green beer was around as early as 1914, but other green beers appeared at the same time or slightly earlier.

In 1910, the Spokane Press used a headline to shout, "Green Beer Be Jabbers!" ("be jabbers" is an excited swear). According to the paper, the First Avenue Bar served the beer to patriotic Irishmen and anybody else who wanted to drink a green brew. Whoever wrote about it had clearly been drinking some green beer:

The practice grew, but not that quickly: in 1926, the Washington Post still called it "an anomalous concoction."

By the '50s, green beer was a mainstream symbol of a holiday that was becoming less specifically Irish and more American. The tradition spread across the country, and bartenders caught on that it was easy to make green beer and even easier to drink it. Eventually, the beverage became so popular that it went international, too. As late as 1985, United Press International reported that the Irish were still being introduced to the delicious, unusual drink made in their honor.

It was an impressive turnaround for green beer, since the term used to be synonymous with beer that wasn't ready to be consumed.

Green beer used to make you sick ... and not in the way you think

Green beer wasn't always the distinguished treat it is today — in fact, it used to make you sick.

"Green beer" is a term brewers still use today to describe beer that's too young (or "green"). As described by Serious Eats, green beer still contains acetaldehyde, which can make beer taste bad because it's not yet fully fermented.

It was such a big problem in the late 1800s and 1910s that beer companies leapt on the idea of "green beer" to promote their own products. Beer companies warned against the "biliousness" that could come from drinking green beer. Schlitz even used the impressive slogan "Schlitz is Old Beer" to convince drinkers its beer wasn't green:

Was green beer actually a problem? Maybe. In 1922, the Washington Times found a chemist who said "green beer is extremely bad on the stomach." Fortunately, though brewers still use the term today, underaged beer is less likely to make it into your stomach because beer production is better understood and regulated.

That said, green-dyed beer still has the power to make you sick — you just have to drink too much of it.