By KELLY MCCARTHY, ABC News

(NEW YORK) — As people prepare to dig into their favorite Halloween candy, there’s one treat with a new consumption warning for adults.

According to the U.S. Food and Drug Administration, eating black licorice in excessive amounts can prompt low potassium levels and trigger a series of irregularities and health issues.

“If you’re 40 or older, eating 2 ounces of black licorice a day for at least two weeks could land you in the hospital with an irregular heart rhythm or arrhythmia,” the FDA said in a statement about the candy that contains glycyrrhizin (glycyrrhizic acid) — the sweetening compound derived from licorice root.

Alexandra Lambert, D.O., M.P.H., an ABC News Medical Unit contributor, explained that the compound can be found in other candies and supplements, but it’s most commonly seen in the old-school candy with a distinct anise aroma.

“This case may be an extreme example of the deleterious effects of black licorice as there are not many other cases in the literature,” Lambert added.

“Not all licorice-flavored foods contain this compound,” she said. “Glycyrrhizin can cause low potassium levels in the body which can lead to abnormal heart rhythms, high blood pressure, swelling, lethargy and congestive heart failure in some people.”

In some cases, Lambert added, abnormal heart rhythms could be fatal.

While many products with licorice don’t disclose how much of it is contained per ounce, the FDA regulates that soft candy can only contain up to 3.1% glycyrrhizic acid.

Black licorice can “interact with some medications, herbs and dietary supplements,” Lambert continued. “Experts believe that potassium levels usually return to normal without causing permanent health problems when consumption of black licorice stops.”

According to the National Institutes of Health, the root of the low-growing shurb that’s native to South Africa has a “long history of use as a folk or traditional remedy in both Eastern and Western medicine.”

Although the NIH cites some cases of use for treatment of heartburn, stomach ulcers, bronchitis, sore throat, cough and some infections caused by viruses, the agency said, “there are insufficient data available to determine if licorice is effective in treating any medical condition.”

For big black licorice fans, the FDA recommends the following advice: “No matter what your age, don’t eat large amounts of black licorice at one time. 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 health care provider. Black licorice can interact with some medications, herbs and dietary supplements. Consult a health care professional if you have questions about possible interactions with a drug or supplement you take.”

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