How exactly is green beer made for St. Patrick’s Day?

St. Patrick’s Day is a holiday that comes with a lot of traditions: corned beef and cabbage, Irish soda bread, lots of drinking, and, of course, green beer. It’s not enough to have a Guinness or any other type of Irish beer on March 17th — you should be drinking green beer, because what better way is there to celebrate the holiday? The only thing is that there’s something about the unnatural hue of this type of beer that makes you wonder: uh, how is green beer made? If you can’t help but feel curious about how green beer is made for St. Patrick’s Day, you’re not alone.

Let’s start this off by clarifying something: green beer isn’t a new trend, something made for Instagram photos and Snapchat Stories. It’s actually been around for over 100 years, and was created by a doctor. In 1914, Dr. Thomas Curtin, a coroner’s physician and eye surgeon, made the first green beer at a St. Patrick’s Day party in the Bronx. He didn’t get specific about what was in his recipe, unfortunately.

However, it kind of seems like green beer had been around even longer than that. A book called Alcohol and Temperance in Modern History says that there’s a centuries-old Irish custom known as “drowning the shamrock” that involves people adding green shamrocks to their beers on St. Paddy’s Day. Did the shamrocks turn the beer green? Is this what Dr. Curtin added to his own recipe? Is this what is still added to beer to make it green today?

I can’t tell you the answers to the first two questions, but I can answer the last: no, green beer today is not made from actual green shamrocks.

Actually, according to Food and Wine, it’s usually made with blue food coloring. That’s because blue balances out the yellowish hue of beer, creating a green color. Some brands make green beer with spriulina, which is a blue-green algae that is very bright. And a lot of people recommend using green food coloring as well.

Just beware: a lot of blue food coloring might make you feel pretty gross. One gastroenterologist told Fox News that green dye can make you sick. Dr. Partha Nandi said, “If you’re just drinking green beer and snacks one day of the year, a few drops of the dye should not make any difference to your health. [But] you may experience some GI distress with diarrhea.”

Yikes. If you want to try to stay on the healthier side, you can make it with wheatgrass or matcha.

If you’re just enjoying one or two green beers to be festive, we think you should be okay — whether it’s made with blue dye or not. Just stay safe out there!