Side effects of licorice may include high blood pressure, paralysis, weakness and occasionally brain damage. These side effects are possible when licorice is consumed in large amounts for several weeks.
Licorice is often used to flavor foods or as an herbal supplement. It is used to alleviate sore throat pain, coughs, chronic fatigue syndrome and digestive ailments, including stomach ulcers and heartburn. Applying licorice to affected areas of the skin has shown improvement in symptoms of eczema.
However, there have been reports of allergic reactions to licorice, which include swelling of the lips, face and tongue and difficulty breathing. Large amounts taken over a long period of time, generally in excess of four weeks, can also lead to low potassium levels. In people who have heart disease, using only 5 grams of licorice a day can cause these side effects. Licorice can also cause fatigue, water retention and headaches.
Women who are pregnant should avoid large amounts of licorice, as it may cause early delivery or miscarriage. Those awaiting surgery should also avoid licorice because it may affect blood pressure during and after the procedure. The FDA has not evaluated licorice, as of 2015, so all potential side effects may not be known. No standards for manufacturing licorice have been set, as of 2015.