Black licorice contains glycyrrhiin .which can cause potassium levels in the body to fall,potentially leading to abnormal heart  rhythms.For people age 40 and above two ounces a day for more then two weeks may trigger arrhythmia-irregular heartbeat–other cardiovascular effects.A regular black licorice habit also may interact with some medicines,herbs. and dietary supplements.Occasional enjoyment is fine.
Tom Rossi RPH (consulting pharmacist)