A 10-year-old boy in Bologna, Italy was hospitalized after he had multiple seizures. Doctors tested his blood and vital signs and were puzzled over the fact that despite his youth, he had high blood pressure and dangerously high levels of cortisol, the body's primary stress hormone. It wasn't until they asked about his brown teeth that they discovered the problem's root cause: the boy had been eating 20 licorice toffees every day for four months. Black licorice gets its natural sweetness from an acid called glycyrrhizin, which can have the unfortunate side effect of depleting the body's levels of potassium, a chemical that's essential for normal heart activity. Though the example from Italy shows that black licorice can be risky for any age, it's most dangerous for those over 40. According to the FDA, older people who consume a 2-ounce bag of black licorice every day for only two weeks can suffer from abnormal heart rhythms, hypertension, edema, and congestive heart failure. Although cutting the treat out of your diet will usually solve the problem, if you're a regular black licorice consumer and experience any of these symptoms, it's a good idea to call your doctor.