Licorice

The medicinally used part of licorice is the root and dried rhizome of the low-growing shrub Glycyrrhiza glabra . Currently, most licorice is produced in Greece, Turkey, and Asia.

Licorice has been used in ancient Greece, China, and Egypt, primarily for gastritis (inflammation of the stomach) and ailments of the upper respiratory tract. Ancient Egyptians prepared a licorice drink for ritual use to honor spirits of the pharaohs. Its use became widespread in Europe and Asia for numerous indications.

In addition to its medicinal uses, licorice has been used as a flavoring agent, valued for sweetness (glycyrrhizin, a component of licorice, is 50 times sweeter than table sugar). The generic name "glycyrrhiza" stems from ancient Greek, meaning "sweet root." It was originally used as flavoring for licorice candies, although most licorice candy is now flavored with anise oil. Licorice is still used in sub-therapeutic doses as a sweetening agent in herbal medicines, lozenges, and tobacco products (doses low enough that significant adverse effects are unlikely).

Licorice has a long history of medicinal use in Europe and Asia. At high doses, there are potentially severe side effects, including hypertension (high blood pressure), hypokalemia (low blood potassium levels) and fluid retention. Most adverse effects have been attributed to the chemical component glycyrrhiza (or glycyrrhizic acid). Licorice can be processed to remove the glycyrrhiza, resulting in DGL (deglycyrrhizinated licorice), which does not appear to share the metabolic disadvantages of licorice.

Synonyms

Bois doux (French), Fabaceae (family), gan cao, glabrene, glabridin, glucoliquiritin, glycyrrhetenic acid, glycyrrhiza, Glycyrrhiza glabra , Glycyrrhiza uralensis Fisher, glycyrrhizin, isoflavan, isoliquiritigenin, kanzo (Japanese), LA, Lakrids (Danish), Lakritzenwurzel (German), leguminose, licochalcone-A, licorice root, Liquiritiae radix, Liquiritia officinalis, liquirizia (Italian), liquorice, prenyllicoflavone, radix glycyrrhizae, réglisse (French), shao-yao-gan-cao-tang (Shakuyanu-kanzo-tou), STW 5-11 (extracts from bitter candy tuft, matricaria flower, peppermint leaves, caraway, licorice root and lemon balm), Suβholzwurzel, sweet root, sweet wood, yashimadhu (Sanskrit).

Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidence	Grade^*
Apthous ulcers / canker sores Some research suggests that licorice extracts, DGL and the drug carbenoxolone may provide benefits for treating cankers sores. However, studies have been small, with flaws in their designs. The safety of DGL makes it an attractive therapy if it does speed healing of these sores, but it is not clear at this time whether there is truly any benefit.	C
Atopic dermatitis Topical licorice extract gel has been shown to be effective in the treatment of atopic dermatitis in preliminary human study. Further research is needed to confirm these results.	C
Bleeding stomach ulcers caused by aspirin Although there has been some study of DGL in this area, it is not clear what effects DGL has on gastrointestinal bleeding.	C
Familial Mediterranean Fever (FMF) Early study of a multi-ingredient preparation containing licorice, called Immunoguard, suggests possible effects in managing FMF. Well-designed study of licorice alone is necessary before a recommendation can be made.	C
Herpes simplex virus Laboratory studies have found that DGL may hinder the spread and infection of herpes simplex virus. Studies in humans have been small, but they suggest that topical application of carbenoxolone cream may improve healing and prevent recurrence.	C
High potassium levels resulting from abnormally low aldosterone levels In theory, because of the known effects of licorice, there may be some benefits of licorice for high potassium levels caused by a condition called hypoaldosteronism. There is early evidence in humans in support of this use. However, research is preliminary and a qualified health care provider should supervise treatment.	C
Peptic ulcer disease Licorice extracts, DGL and carbenoxolone have been studied for treating peptic ulcers. DGL (but not carbenoxolone) may offer some benefits. However, most studies are poorly designed and some results conflict. Therefore, it is unclear whether there is any benefit from licorice for this condition.	C
Reducing body fat mass Preliminary data shows that licorice may reduce body fat mass. Further research is needed to confirm these results.	C
Viral hepatitis The licorice extracts DGL and carbenoxolone have been proposed as possible therapies for viral hepatitis. Further research is needed before a recommendation can be made.	C
Genital herpes Available studies have not found any benefit from carbenoxolone cream when applied topically to the skin to treat genital herpes infections.	D

*Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use;
F: Strong scientific evidence against this use.

Grading rationale

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Adrenal insufficiency (Addison's disease), allergy, antibacterial, antimicrobial, antioxidant, antispasmodic, antitumor, aplastic anemia, asthma, bacterial infections, bad breath, breast cancer, bronchitis, cancer, chronic fatigue syndrome, colitis, colorectal cancer, constipation, coronavirus, cough, cysts, dental hygiene, depression, detoxification, diabetes, diuretic, diverticulitis, dysmenorrhea (painful menstruation), eczema, Epstein-Barr virus, fever, functional dyspepsia, gastroesophageal reflux disease, gentamicin induced kidney damage, graft healing, hepatoma, high cholesterol, HIV, hormone regulation, hot flashes, hyperpigmentation disorders, immune system stimulation, inflammation, inflammatory skin disorders, laryngitis, liver cancer, liver protection, lung cancer, melanoma, melasma, menopausal symptoms, metabolic abnormalities, methicillin-resistant staphylococcus aureus (MRSA), muscle cramps, obesity, osteoarthritis, plaque, polycystic ovarian syndrome, prostate cancer, pruritus (rash), rheumatoid arthritis, RSV, SARS, skin disorders, sore throat, stomach upset, tobacco-associated lung cancer, urinary tract inflammation.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older):

Carbenoxolone gel or cream: A 2 percent cream or gel has been applied five times a day for seven to 14 days for herpes simplex virus skin lesions.

Commercial preparation : 3. 5 grams a day of a commercial preparation of licorice has been studied for body fat mass reduction.

DGL extract tablets: Doses of 380 to 1,140 milligrams three times daily taken by mouth 20 minutes before meals have been used.

Licorice fluid extract (10 percent to 20 percent glycyrrhizin): Doses of 2 to 4 milliliters per day have been taken by mouth.

Licorice powdered root (4 percent to 9 percent glycyrrhizin): Doses of 1 to 4 grams taken by mouth daily, divided into three or four doses, have been used.

Children (younger than 18 years):

There is not enough scientific evidence to recommend licorice for use in children, and licorice is not recommended due to potential side effects.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

People should avoid licorice if they have a known allergy to licorice, any component of licorice or any member of the Fabaceae (Leguminosae) plant family (pea family). There is a report of rash after applying a cosmetic product containing licorice to the skin.

Side Effects and Warnings

Licorice contains a chemical called glycyrrhizic acid, which is responsible for many of the reported side effects. DGL (deglycyrrhizinated licorice) has had the glycyrrhizic acid removed, and therefore is considered safer for use.

Many of the adverse effects of licorice result from actions on hormone levels in the body. By altering the activities of certain hormones, licorice may cause electrolyte disturbances. Possible effects include sodium and fluid retention, low potassium levels, and metabolic alkalosis.

Electrolyte abnormalities may also lead to irregular heartbeats, heart attack, kidney damage, muscle weakness, or muscle breakdown. Licorice should be used cautiously by people with congestive heart failure, coronary heart disease, kidney or liver disease, fluid retention (edema), high blood pressure, underlying electrolyte disturbances, hormonal abnormalities, or those taking diuretics.

Hormonal imbalances have been reported with the use of licorice, such as abnormally low testosterone levels in men or high prolactin levels and estrogen levels in women. However, study results conflict. These adverse effects may reduce fertility or cause menstrual abnormalities.

Reduced body fat mass has been observed with the use of licorice. Acute pseudo-aldosteronism syndrome has been associated with licorice. Paralysis has been reported in a patient taking licorice that contributed to low potassium levels. Thyrotoxic periodic paralysis (TPP) has been associated with licorice. Metabolic alkalosis and seizure has been reported from licorice in antacid.

Licorice has been reported to cause high blood pressure, including dangerously high blood pressure with symptoms such as headache, nausea, vomiting, and hypertensive encephalopathy with stroke-like effects (for example, one-sided weakness).

High doses of licorice may cause temporary vision problems or loss. Ocular side effects have been reported. Central retinal vein occlusion has been associated with licorice. A case report exists of licorice-induced hypokalemia associated with dropped head syndrome (DHS).

Pregnancy and Breastfeeding

Licorice cannot be recommended during pregnancy and breast-feeding due to possible alterations of hormone levels and the possibility of premature labor.

Hormonal imbalances reported with the use of licorice include abnormally low testosterone levels in men and high prolactin levels/estrogen levels in women. However, study results conflict. 17-OHP and LH levels may also be affected.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

In general, prescription drugs should be taken one hour before licorice or two hours after licorice because licorice may increase the absorption of many drugs. Increased absorption may increase the activities and side effects of some drugs (for example, nitrofurantoin). Phosphate salts have been shown to increase licorice absorption. Liver metabolism of certain drugs may be affected by licorice but further study is needed before a conclusion can be drawn.

Because the toxicity of digoxin (Lanoxin®) is increased when potassium levels are low, people who take digoxin and are interested in using licorice should discuss this with their health care provider. Increased monitoring may be necessary. Other drugs that may increase the tendency for irregular heart rhythms are also best avoided when using licorice.

Licorice may reduce the effects of blood pressure or diuretic (urine-producing) drugs, including hydrochlorothiazide and spironolactone. Use of licorice with the diuretics hydrochlorothiazide or furosemide (Lasix®) may cause potassium levels to fall very low and lead to dangerous complications. Other drugs that can also cause potassium levels to fall too low and are best avoided when using licorice include insulin, sodium polystyrene (Kayexalate®), and laxatives. Chewing tobacco may increase the toxicity of licorice gums by causing electrolyte disturbances.

Licorice may increase the adverse effects associated with corticosteroids such as prednisolone, and monoamine oxidase inhibitors such as Isocarboxazid (Marplan®), phenelzine (Nardil®), or tranylcypromine (Parnate®). Agents acting on serotonin may also interact with licorice.

Licorice may reduce the effects of birth control pills, hormone replacement therapies, or testosterone therapy.

In theory, licorice may increase the risk of bleeding when used with anticoagulants (blood thinners) or antiplatelet drugs. Examples include warfarin (Coumadin®), heparin, clopidogrel (Plavix®), or aspirin.

Interactions with Herbs and Dietary Supplements

Herbs with potential laxative properties may add to the potassium lowering effects of licorice.

Herbs with potential diuretic properties may increase adverse effects associated with licorice.

Herbs and supplements that lower blood pressure may add to the blood pressure lowering effects of licorice.

Herbs with monoamine oxidase inhibitor activity may cause worse side effects when used at the same time as licorice.

In theory, herbs and supplements that increase the risk of bleeding may further increase the risk of bleeding when taken with licorice.

Liver metabolism of certain herbs and supplements may be affected by licorice but further study is needed before a conclusion can be drawn.

Licorice (Glycyrrhiza glabra L.) and DGL (deglycyrrhizinated licorice)

Background

Synonyms

Evidence

Dosing

Safety

Interactions