What Is Wormwood and What Does It Do to Absinthe?

Despite its resurgence in the modern cocktail movement through drinks like the Sazerac, there’s no getting around absinthe’s reputation as a hallucinogenic liquor. It’s not hallucinogenic, but that doesn’t stop associations with green fairies. The reason for that reputation stems from a single ingredient in absinthe: wormwood.

The plant is native to Europe, and its leaves are used for flavoring a range of things, but its most famous association is with absinthe. The scientific name for common wormwood, Artemisia absinthium, gave birth to the spirit’s name.

Wormwood’s bitter reputation is thousands of years old. The first written record of a medicinal use for wormwood can be found on Egyptian papyrus dating back to around 1552 B.C. Ancient Greek philosophers like Pythagoras and Hippocrates recommended wormwood to be used for everything from childbirth to rheumatism. In the book of Revelations in the Bible, wormwood is used to symbolize a fallen star that turns a third of the world’s water too bitter to drink. Shakespeare referenced wormwood in Romeo and Juliet by writing that Juliet’s wet nurse weaned her by using wormwood.

What’s too bitter and medicinal for some, however, is delicious to others. In the late 1700s, a Swiss woman by the name of Madame Henriod used the plant as a bitter and herbaceous flavoring agent in her liquor. The leaves are silky and the plant has droopy yellow flower heads. When steeped in a liquid, it imparts a vibrant green color.

In 1798, a Swiss distiller named Henri Louis-Pernod created the first commercially produced absinthe that used wormwood as a major flavor component. Pernod’s operations moved to Pontarlier, France, in 1805, and the drink exploded in popularity among artists and the upper class over the next century. It became so common that there was a “green hour” in Paris that referred to when people sat outdoors and sipped the drink. The trend caught on in the U.S. and the rest of Europe, but was short lived. In 1879, Harper’s Weekly claimed that “many deaths are directly traceable to the excessive use of absinthe,” a story in The New York Times reported. It continued that, “A regular absinthe drinker seldom perceives that he is dominated by its baleful influence until it is too late. All of a sudden he breaks down; his nervous system is destroyed, his brain is inoperative, his will is paralyzed, he is a mere wreck; there is no hope of his recovery.”

In the minds of people who blamed absinthe for societal ills, one ingredient was responsible: wormwood. It was the ingredient that most defined the spirit, and a study in 1910 explicitly blamed wormwood. The study specifically targeted a volatile compound in the plant called thujone, which can impact the central nervous system and can cause seizures. Belgium banned absinthe in 1905, followed by Switzerland (1908), Holland (1910), the U.S. (1912) and finally France in 1915. Spain was the only European country that kept the spirit legal.

The ban on absinthe, and all things wormwood, lasted for decades. It wasn’t until 1988 that countries in Europe started realizing that the ban was based on a misconception. All wormwood does to absinthe is add aromatics and flavor. There isn’t enough wormwood or thujone in absinthe to cause seizures or other negative health effects. That is true now, but was also true at the time of the ban—tests on pre-prohibition absinthe found that most of the old spirits also lacked enough thujone to negatively impact someone’s health. It’s understood today that the health problems were due to overconsumption of a high-alcohol spirit, not because of wormwood and thujone.

In 2007, the U.S. adjusted the amount of thujone that it considers safe for consumption. The change allows absinthe to have 10 parts per million or less of thujone. Modern absinthe once again uses wormwood, giving the spirit that iconic green color, herbaceous aroma and strong bitterness.