(CNN) If Halloween is your excuse for endlessly indulging in candy (and of course it is), go slow on the black licorice.

Just as it does each Halloween, the Food and Drug Administration has posted a reminder on its website urging folks to keep their black licorice consumption to a minimum

The reasoning? Too much of the old-fashioned favorite can cause health problems such as irregular heart rhythm, especially in people over 40.

Black licorice contains a sweetening compound called glycyrrhizin, which can cause a drop in potassium levels. With low levels, some people might experience high blood pressure, swelling and even congestive heart failure, the FDA says.

The good news is that potassium levels return to normal after you stop eating copious amounts of black licorice.

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