Too much black licorice can result in abnormal heart rhythms and hypertension.
Did you know you can overdose on black licorice? The U.S. FDA issued a warning encouraging moderation if you enjoy snacking on it: regardless of age, don't eat large amounts at one time. Most people should limit consumption to no more than 2 ounces per day. A naturally occurring compound in the licorice root called, glycyrrhizin, depletes potassium levels which can lead to cardiac arrhythmia, hypertension, or lethargy.
PositiveTip: Use caution in eating too much of the leftover Halloween candy!