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Licorice is an herb that grows in parts of Europe and Asia. The root is used as medicine. Licorice root contains glycyrrhizin, which is also called glycyrrhizic acid. Glycyrrhizin can cause adverse effects when eaten in large quantities. Many "licorice" products manufactured in the U.S. actually don't contain any licorice. Instead, they contain anise oil, which has the characteristic smell and taste of "black licorice".

Licorice is used for eczema, swelling (inflammation) of the liver (hepatitis), mouth sores, and many other conditions, but there is no good scientific evidence to support most of these uses.

Licorice is also used to flavor foods, beverages, and tobacco products.

Coronavirus disease 2019 (COVID-19): Some experts warn that licorice may interfere with the body's response against COVID-19. There is no strong data to support this warning. But there is also no good data to support using licorice for COVID-19. Follow healthy lifestyle choices and proven prevention methods instead.

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
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The chemicals contained in licorice are thought to decrease swelling, thin mucus secretions, decrease cough, and increase the chemicals in our body that heal ulcers.

When taken by mouth: Licorice is LIKELY SAFE for most people when taken in amounts found in foods. Licorice that has had a chemical called glycyrrhizin removed is POSSIBLY SAFE when taken by mouth in larger amounts as medicine. These products are sometimes called deglycyrrhizinated licorice (DGL), and have been used in doses of up to 4.5 grams daily for up to 4 months.

Licorice products that contain glycyrrhizin are POSSIBLY UNSAFE to take in large amounts for more than 4 weeks or in smaller amounts, long-term. Eating licorice 5 grams or more daily for several weeks or longer can cause severe side effects. These include very high blood pressure, low potassium levels, weakness, paralysis, irregular heart rhythms, and heart attack. People who eat a lot of salt or have heart disease, kidney disease, or high blood pressure are more sensitive to licorice. They can have these problems after eating smaller amounts of licorice.

People who chew tobacco flavored with licorice, drink licorice tea, or ingest large amounts of candy or lozenges that contain licorice might develop high blood pressure and other serious side effects.

When applied to the skin: Licorice is POSSIBLY SAFE when a gel with licorice root extract 2% is applied to the skin for up to 2 weeks or when the extract is used in a mouth rinse for up to one week. It may cause a rash in some people.

Special Precautions & Warnings:

Pregnancy and breast-feeding: It is UNSAFE to take licorice by mouth if you are pregnant. High consumption of licorice during pregnancy, about 250 grams of licorice per week, seems to increase the risk of early delivery. It might cause a miscarriage or early delivery. There isn't enough reliable information available about the safety of taking licorice when breast-feeding. Stay on the safe side and avoid use.

Heart disease: Licorice can cause the body to store water, and this can make congestive heart failure worse. Licorice can also increase the risk of irregular heartbeat. Don't consume licorice if you have heart disease.

Hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Licorice might act like estrogen in the body. If you have any condition that might be made worse by exposure to estrogen, don't use licorice.

High blood pressure: Licorice can raise blood pressure. Don't consume large amounts of it if you have high blood pressure.

A muscle condition caused by nerve problems (hypertonia): Licorice can cause the level of potassium to drop in the blood. This can make hypertonia worse. Avoid licorice if you have hypertonia.

Low potassium levels in the blood (hypokalemia): Licorice can lower potassium in the blood. If your potassium is already low, licorice might make it too low. Don't use licorice if you have this condition.

Kidney disease: Overuse of licorice could make kidney disease worse. Don't use it.

Sexual problems in men: Licorice can lower a man's interest in sex and also worsen erectile dysfunction (ED) by lowering levels of a hormone called testosterone.

Surgery: Licorice might interfere with blood pressure control during and after surgery. Stop taking licorice at least 2 weeks before a scheduled surgery.

Digoxin (Lanoxin)

Interaction Rating=Moderate Be cautious with this combination.

Large amounts of licorice can decrease potassium levels in the body. Low potassium levels can increase the side effects of digoxin (Lanoxin).

Estrogens

Interaction Rating=Moderate Be cautious with this combination.

Licorice seems to change hormone levels in the body. Taking licorice along with estrogen pills might decrease the effects of estrogen pills.

Some estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

Ethacrynic Acid (Edecrin)

Interaction Rating=Moderate Be cautious with this combination.

Licorice can cause the body to get rid of potassium. Ethacrynic acid (Edecrin) can also cause the body to get rid of potassium. Taking licorice and ethacrynic acid (Edecrin) together might cause potassium to become too low.

Furosemide (Lasix)

Interaction Rating=Moderate Be cautious with this combination.

Licorice can cause the body to get rid of potassium. Furosemide (Lasix) can also cause the body to get rid of potassium. Taking licorice and furosemide together might cause the potassium levels in your body to go too low.

Medications changed by the liver (Cytochrome P450 2B6 (CYP2B6) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver.

Licorice might decrease how quickly the liver breaks down some medications. Taking licorice along with some medications that are broken down by the liver can increase the effects and side effects of some medications. Before taking licorice talk to your healthcare provider if you take any medications that are changed by the liver.

Some of these medications changed by the liver include ketamine (Ketalar), phenobarbital, orphenadrine (Norflex), secobarbital (Seconal), dexamethasone (Decadron), and others.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver.

Licorice might change how the liver breaks down some medications. Taking licorice along with medications that are broken down by the liver might increase or decrease the effects of these medications. Before taking licorice, talk to your healthcare provider if you are taking any medications that are changed by the liver.

Some medications changed by the liver include celecoxib (Celebrex), diclofenac (Voltaren), fluvastatin (Lescol), glipizide (Glucotrol), ibuprofen (Advil, Motrin), irbesartan (Avapro), losartan (Cozaar), phenytoin (Dilantin), piroxicam (Feldene), tamoxifen (Nolvadex), tolbutamide (Tolinase), torsemide (Demadex), and warfarin (Coumadin).

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver.

Licorice might change how the liver breaks down some medications. Taking licorice along with medications that are broken down by the liver might increase or decrease the effects of some medications. Before taking licorice, talk to your healthcare provider if you are taking any medications that are changed by the liver.

Some medications changed by the liver include lovastatin (Mevacor), ketoconazole (Nizoral), itraconazole (Sporanox), fexofenadine (Allegra), triazolam (Halcion), and many others.

Medications for high blood pressure (Antihypertensive drugs)

Interaction Rating=Moderate Be cautious with this combination.

Large amounts of licorice seem to increase blood pressure. By increasing blood pressure licorice might decrease the effectiveness of medications for high blood pressure.

Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), amlodipine (Norvasc), hydrochlorothiazide (HydroDIURIL), furosemide (Lasix), and many others.

Medications for inflammation (Corticosteroids)

Interaction Rating=Moderate Be cautious with this combination.

Some medications for inflammation can decrease potassium in the body. Licorice might also decrease potassium in the body. Taking licorice along with some medications for inflammation might decrease potassium in the body too much.

Some medications for inflammation include dexamethasone (Decadron), hydrocortisone (Cortef), methylprednisolone (Medrol), prednisone (Deltasone), and others.

Warfarin (Coumadin)

Interaction Rating=Major Do not take this combination.

Warfarin (Coumadin) is used to slow blood clotting. The body breaks down warfarin (Coumadin) to get rid of it. Licorice might increase the breakdown and decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.

Water pills (Diuretic drugs)

Interaction Rating=Moderate Be cautious with this combination.

Large amounts of licorice can decrease potassium levels in the body. "Water pills" can also decrease potassium in the body. Taking licorice along with "water pills" might decrease potassium in the body too much.

Some "water pills" that can deplete potassium include chlorothiazide (Diuril), chlorthalidone (Thalitone), furosemide (Lasix), hydrochlorothiazide (HCTZ, HydroDIURIL, Microzide), and others.

Grapefruit: Drinking grapefruit juice when taking licorice might increase licorice's ability to cause potassium depletion.
Herbs that contain cardiac glycosides: Using too much licorice can decrease potassium in the body. This can damage the heart. Using licorice with herbs that can damage the heart might make this effect worse. Herbs that might damage the heart include digitalis, lily-of-the-valley, pheasant's eye, and squill.
Methoxylated flavones: Methoxylated flavones are a type of chemical found in plants such as citrus. Some people take them as medicine. Taking licorice with methoxylated flavones might decrease how much methoxylated flavones are in the blood.
Stimulant laxative herbs: Using too much licorice can decrease potassium in the body. Herbs that have a stimulant laxative effect can also lower potassium in the body. Using licorice along with these herbs can increase the risk of lowering potassium levels too much. Stimulant laxative herbs include aloe vera, alder buckthorn, European buckthorn, cascara sagrada, castor oil, rhubarb, and senna.

Salt-containing foods: Licorice use can increase sodium and water retention and increase blood pressure. Also, eating a lot of salt can make the side effects of licorice even worse.

The following doses have been studied in scientific research:

APPLIED TO THE SKIN:

  • For eczema (atopic dermatitis): Gel products containing 1% or 2% licorice root extract have been applied three times daily for 2 weeks.
  • For canker sores: An oral patch containing licorice 0.015-0.229 mg/kg has been used 16 hours daily for 8 days. A patch containing 1% licorice extract has been used. A mouth rinse containing 5% licorice extract has been swished around the mouth for about 3 minutes four times daily until healing. Warm water containing deglycyrrhizinated licorice powder 200 mg has been gargled four times daily for 7 days.
  • For side effects in people with a breathing tube: A lozenge containing 97 mg of licorice has been sucked for 30 minutes before anesthesia. Gargling with 30 mL of a fluid containing 0.5 grams of licorice for at least one minute beginning 5 minutes before placement of a breathing tube, has been used.

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