Trick or Treat: Don’t Eat Too Much Black Licorice on Halloween, Warns FDA

It’s that time of year again when ghoulish children turn up at your door, demanding payment in candy or threatening a sinister trick instead.

But if you’re keeping a bowl of sweets on stand-by, you might want to leave out the black licorice.

The U.S. Food and Drug Administration (FDA) has issued a warning ahead of Halloween—which it describes as the “biggest candy eating holiday of the year”—urging people not to overdo it on the medicinal-tasting candy or potentially face heart problems.

1031_Black_licorice Mariette Le Roux Concorp factory managing director Jurgen van Krevel shows fresh licorice in Jirnsum, the Netherlands, on November 4, 2008. ANOEK DE GROOT/AFP/Getty

The problem is caused by glycyrrhizin—a sweetening compound derived from the root of licorice, a low-growing shrub that is found most in Greece, Turkey and Asia. When consumed in large amounts, glycyrrhizin can prompt potassium levels in the body to fall. Low potassium can lead to a variety of health issues, particularly abnormal heart rhythms, but also high blood pressure, swelling, lethargy, and even congestive heart failure.

The FDA warned that, for people 40 years old or over, eating two ounces of black licorice a day for two weeks can result in arrhythmia, or irregular heart rhythm. Potassium levels usually return to normal with no permanent health problems when a person stops eating it, according to the FDA’s Linda Katz.

But no matter what the age of the consumer, black licorice can have a negative impact on health. The FDA said that no one should eat large amounts in one sitting, and that if they experience irregular heartbeat or muscle weakness, they should stop immediately and consult a doctor.

Read more: Boy has seizure after eating too much licorice

Black licorice can also interact with medications, herbs and dietary supplements, it warned.

The sweet has long been divisive. Many people dislike black licorice for its similarity to medicines like NyQuil, but the sweet has a massive fanbase in Europe, particularly in the Netherlands (although the Dutch varieties are often saltier than what American consumers are used to.)

And the FDA’s warning is not the first time health risks have been associated with black licorice. In 2012, the American Licorice Company announced it was pulling its Red Vines black licorice twists after they tested positive for high levels of lead.