When it comes to candy preferences, black licorice might be just as divisive as candy corn.

But on the eve of Halloween, the Food and Drug Administration (FDA) has struck terror in the hearts of black licorice eaters of a certain age by posting a formal warning about the chewy candy.

On Monday, the FDA issued a consumer update advising candy eaters who are 40 years of age or older to limit their gorging of black licorice to a maximum of two ounces (about three 1-inch pieces) a day — or risk hospitalization from an irregular heart rhythm or arrhythmia.

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Too much black licorice won't just turn your teeth black. It might be bad for your heart, too. Getty Images Stock

The agency's experts determined that the candy contains enough of the sweetening compound glycyrrhizin — derived from the licorice root — to significantly lower the body's potassium levels.

The effects in the parents who pilfer their children's trick-or-treat hauls can be anything but sweet — including abnormal heart rhythms, elevated blood pressure levels, edema and even congestive heart failure, in extreme cases.

Several studies in medical journals have also found that, regardless of age, people with a history of heart disease or high blood pressure are particularly susceptible to the effects of glycyrrhizin when ingested.

So those at a greater risk should eat these delicious slime-filled spider treats in moderation, for example.

Or if you just have to eat something chewy and sweet, munch down on this simple dessert delicacy of Twinkie hotdogs, that use a little bit of red licorice as a literal and figurative garnish.

There is good news, however. Usually after black licorice is consumed, potassium levels go back to normal and there tend to be no lasting health effects once the person stops eating it.

Regardless of age, the FDA has issued the following guidelines when it comes to eating licorice: