Black licorice has been a favorite confection for thousands of years. According to Healthline, licorice root, which is used as a sweetener in many candies and beverages, has been used for its medicinal benefits for centuries. The ancient Egyptians used licorice root in tea to soothe gastrointestinal problems. The glycyrrhizic acid in licorice boasts anti-inflammatory and immune-boosting properties.

Licorice is also touted as an excellent treatment for respiratory problems, reducing stress and assisting in the treatment of both breast and prostate cancers, according to ongoing research by the American Cancer Society. Topically, gels containing licorice can help treat eczema because of its antibacterial properties. Many holistic health practitioners suggest applying licorice to tooth decay to kill bacteria.

But the FDA has issued a stern warning if you are 40 years or older, eating two ounces of black licorice a day for at least two weeks could land you in the hospital with an irregular heart rhythm or arrhythmia.

Glycyrrhizic acid can cause potassium levels in the body to plummet. When that happens, some folks experience abnormal heart rhythms, high blood pressure, edema or swelling, lethargy, and congestive heart failure.

FDA's Linda Katz, M.D., says potassium levels are usually restored when people stop eating black licorice.

"No matter what your age, do not eat large amounts of black licorice at one time," she says. "If you have been eating a lot of black licorice and have an irregular heart rhythm or muscle weakness, stop eating it immediately and contact your healthcare provider."

Black licorice can also interact with other medication, herbs, and dietary supplements. Consult a healthcare professional if you have any questions about possible interactions with a product you take.

There is good news for licorice lovers: According to the Food Network, red licorice is safe to consume.