Licorice is not just a candy flavoring. It is an herb used in supplement form for respiratory, digestive and skin conditions. Licorice contains a substance called glycyrrhizin, which appears to be responsible for a host of side effects sometimes called licorice toxicity. A glycyrrhizin-free version of licorice is available and often used in treatment, but certain pre-existing conditions make licorice off-limits without doctor consent and monitoring.
The University of Maryland Medical Center warns that an overdose of licorice that contains glycyrrhizin can lead to sensitivity to an adrenal hormone. The condition, known as pseudoaldosteronism, can create secondary side effects of high blood pressure, edema and more. The center notes this can appear in people taking more than 20 g of licorice each day. People with pre-existing conditions such as high blood pressure can develop pseudoaldosteronism by taking only 5 g each day. The center notes standard doses tend to be below 500 mg. Limit your use of licorice to less than a month and a half, and have your doctor keep track of your use and your health.
Blood, Liver and Kidney
If you have any problems with blood pressure, edema, heart disease, liver disease or kidney disease, do not take licorice. It can lead to these conditions developing in healthy people, so if you are already dealing with any blood, heart, liver or kidney issues, you risk making them worse.
Hormonal Side Effects
Licorice has an apparent effect on your body’s hormones, especially estrogen. MedlinePlus notes it can adversely interact with birth control and hormone replacement pills, possibly blocking their effects. Licorice can actually behave like an estrogen, requiring precaution among those who have had hormone-sensitive cancers. It can also interact with prednisone, a steroid.
Licorice can lead to electrolyte imbalances by depleting potassium and increasing the level of sodium in the blood. This will enhance the effect of potassium-depleting drugs you may be taking; if you already have low blood potassium or hypokalemia, licorice can make it much worse. It can also lead to the development of hypertonia, a condition in which muscles resist stretching.
Be aware that licorice candy and other products are risky if they are flavored with natural licorice because they contain glycyrrhizin. A 2009 case history from the "Canadian Journal of Emergency Medicine" noted that eating naturally flavored licorice candy was enough to induce edema and high blood pressure in a 49-year-old patient with no previous health problems. The authors of the case history say candy, drinks, cough drops, throat lozenges, tobacco, tea, gum and other herbal remedies can contain natural licorice. Any problems with alertness, heartbeat, digestive problems, hives, breathing problems or swelling need to be checked out immediately. You must let your doctor know if you've ingested anything with licorice so he can investigate that as a possible cause. Drugs.com notes that there aren’t really any “common” side effects with licorice, so notify your doctor of anything you experience after taking licorice.