Licorice

The drug is gan cao, the root, and it appears in a very large share of classical formulas. It is used in two forms: raw gan cao drains heat, reduces swelling and resolves toxicity, while honey-fried gan cao (zhi gan cao) is warmer and tonifies Spleen Qi.

Its classical actions include relaxing muscle spasm and alleviating pain. Its best-known role is to harmonise a formula, moderating the harsh actions of other herbs and reconciling ingredients that would otherwise conflict ^{72Reference 72Zeng D · 2003Essentials of Chinese Medicine Materia Medica — traditional medical text}.

In modern Chinese medicine it is also used as a tonic, an antipyretic, an antidote, a demulcent and expectorant for the lungs, for sore throat, cough and asthma, and for acute abdominal pain ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}.

The root is yashtimadhu, sweet in taste with a cooling potency. It is given for cough and sore throat, for gastric complaints, and as a rasayana.

In India, licorice is also taken to ease thirst, as an antitussive and demulcent, and for influenza, uterine complaints and biliousness ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}.

Japanese Kampo carries the Chinese usage over largely intact, and kanzo appears in many Kampo formulas.

Licorice has been used in Europe and the Mediterranean since antiquity. Theophrastus recommended it for asthma and for healing wounds, and Pliny the Elder wrote that it cleared the voice and eased hunger and thirst ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}.

Culpeper boiled it with maidenhair and figs as a drink for dry cough, hoarseness, wheezing, shortness of breath and “all the griefs of the breast and lungs” ^{77Reference 77Culpeper · 1653Liquorice — historical sourceView study →}. He also gave it for pain in the kidneys, painful urination and “heat of urine” ^{77Reference 77Culpeper · 1653Liquorice — historical sourceView study →}.

Nineteenth-century American writers described the root as an emollient, demulcent, expectorant and diuretic ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}. Later uses included Addison’s disease and strengthening the action of glucocorticoids ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}.

In the European Union, licorice root is accepted as a traditional herbal medicine for indigestion with a burning sensation and as an expectorant for a cough with a cold ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

The best human liver evidence is for glycyrrhizin given intravenously. In Japan, Stronger Neo-Minophagen C (SNMC) has been used for chronic hepatitis for decades. In a multicentre double-blind study it lowered ALT more than placebo. In a long-term comparison, cirrhosis developed in 28% of patients on SNMC against 40% of controls at 13 years, and liver cancer in 13% against 25% at 15 years ^{1Reference 1Kumada H · 2002ObservationalLong-term treatment of chronic hepatitis C with glycyrrhizin (SNMC) for preventing liver cirrhosis and hepatocellular carcinoma — cohortView study →}.

A European RCT found that 4 weeks of intravenous glycyrrhizin lowered ALT in hepatitis C patients who had not responded to interferon ^{2Reference 2van Rossum TG et al. · 2001RCTGlycyrrhizin-induced reduction of ALT in European patients with chronic hepatitis C — randomisedView study →}.

For chronic hepatitis B, a network meta-analysis of 53 RCTs found that glycyrrhizic-acid preparations added to entecavir improved ALT, AST and overall response more than entecavir alone ^{3Reference 3Gao W et al. · 2023Meta-analysisComparative effectiveness of glycyrrhizic acid preparations for chronic hepatitis B liver function: a network meta-analysis of 53 RCTsView study →}. A separate meta-analysis of 18 trials of compound glycyrrhizin injection found the trials generally of low methodological quality ^{4Reference 4Wang HN et al. · 2021Meta-analysisSystematic review and meta-analysis of Compound Glycyrrhizin Injection in chronic hepatitis B liver damageView study →}. An open-label RCT showed corticosteroid plus glycyrrhizin improved liver tests and histology in chronic drug- and herb-induced liver injury ^{5Reference 5Wang JB et al. · 2022RCTCorticosteroid plus glycyrrhizin therapy for chronic drug- or herb-induced liver injury: a randomised open-label trialView study →}.

Two randomised trials in non-alcoholic fatty liver disease used oral root extract. In 66 patients, 2 g/day for 2 months lowered ALT and AST ^{6Reference 6Hajiaghamohammadi AA et al. · 2012RCTEfficacy of licorice root extract in decreasing transaminase activities in NAFLD: a randomised controlled trialView study →}. In 60 women following a weight-loss diet, 1 g/day for 12 weeks lowered ALT, insulin resistance and malondialdehyde and improved steatosis on ultrasound ^{7Reference 7Rostamizadeh P et al. · 2022RCTEffects of licorice root supplementation on liver enzymes, steatosis and oxidative stress in women with NAFLD: a randomised double-blind trialView study →}.

Glycyrrhizic acid and its aglycone 18β-glycyrrhetinic acid are credited with the anti-inflammatory effect on the liver.

Gap: the hepatitis evidence is for an injectable, purified glycyrrhizin product, not the root taken by mouth, and that route also causes pseudo-aldosteronism ^{8Reference 8van Rossum TG et al. · 2001Observationalvan Rossum TG, et al. (2001). ‘Pseudo-aldosteronism’ induced by intravenous glycyrrhizin treatment of chronic hepatitis C patients — observational. Journal of Gastroenterology and Hepatology. https://pubmed.ncbi.nlm.nih.gov/11446888/View study →}. The oral fatty-liver trials are small and short.

A systematic review of six trials (314 people) found topical licorice reduced the pain, size and healing time of recurrent aphthous ulcers (canker sores) ^{13Reference 13Dorsareh F et al. · 2023Systematic reviewTopical Licorice for Aphthous: A Systematic Review of Clinical TrialsView study →}. A network meta-analysis of 72 trials of topical treatments ranked glycyrrhiza among the more effective options ^{17Reference 17Liu H et al. · 2022Meta-analysisEfficacy of Topical Intervention for Recurrent Aphthous Stomatitis: A Network Meta-AnalysisView study →}.

In individual RCTs, a licorice gargle juice cut aphthous pain within a day ^{14Reference 14Liu HL et al. · 2022RCTEffective licorice gargle juice for aphthous ulcer pain relief: a randomised double-blind placebo-controlled trialView study →}, adding licorice to a diphenhydramine solution improved on diphenhydramine alone ^{15Reference 15Akbari N et al. · 2020RCTEffects of licorice-containing diphenhydramine solution on recurrent aphthous stomatitis: a double-blind randomised clinical trialView study →}, and a dissolving licorice patch shrank ulcers faster than placebo by day 8 ^{16Reference 16Martin MD et al. · 2008A controlled trial of a dissolving oral patch of glycyrrhiza (licorice) extract for aphthous ulcersView study →}.

The proposed mechanism is local anti-inflammatory and soothing (demulcent) action.

Gap: the trials are small and use different vehicles (patch, film, gargle, elixir), with no standard product or dose.

Gargling a licorice solution before anaesthesia reduces sore throat after surgery. In a double-blind RCT of 236 thoracic-surgery patients intubated with large double-lumen tubes, a gargle of 0.5 g licorice cut sore-throat incidence from 36% to 19% compared with sugar-water ^{9Reference 9Ruetzler K et al. · 2013RCTA randomised, double-blind comparison of licorice versus sugar-water gargle for prevention of postoperative sore throat and postextubation coughingView study →}.

An earlier randomised study in 40 laminectomy patients reported the same direction of effect ^{10Reference 10Agarwal A et al. · 2009RCTEfficacy of licorice gargle for attenuating postoperative sore throat — randomised single-blindView study →}, and a dose-finding RCT compared gargle strengths ^{11Reference 11Honarmand A et al. · 2016RCTEfficacy of different doses of liquorice gargling for attenuating postoperative sore throat and cough after tracheal intubation — randomisedView study →}. A Bayesian network meta-analysis of topical agents for sore throat after intubation included licorice among the effective options ^{12Reference 12Singh NP et al. · 2020Meta-analysisEfficacy of topical agents for prevention of postoperative sore throat after single-lumen intubation: a Bayesian network meta-analysisView study →}.

Gap: the benefit is shown for a gargle before a procedure, and it does not establish that licorice tea helps an ordinary sore throat.

Deglycyrrhizinated licorice (DGL) was tested in controlled trials for gastric and duodenal ulcer from 1969, including a double-blind comparison with cimetidine ^{18,20Reference 18Turpie AG et al. · 1969Clinical trialClinical trial of deglycyrrhizinized liquorice in gastric ulcerView study →Reference 20D’Imperio N et al. · 1978RCTDouble-blind trial in duodenal and gastric ulcers: cimetidine and deglycyrrhizinized liquorice — randomisedView study →}.

DGL also reduced aspirin-induced stomach damage in rats, and reduced faecal blood loss from high-dose aspirin in people ^{19Reference 19Rees WD et al. · 1979Clinical trialEffect of deglycyrrhizinated liquorice on gastric mucosal damage by aspirin — animal and human studyView study →}.

The anti-ulcer action is attributed to glycyrrhetinic acid raising mucosal prostaglandins, which increases mucus secretion and cell renewal. The same idea produced the semi-synthetic drug carbenoxolone.

In Helicobacter pylori infection, adding licorice to clarithromycin-based triple therapy raised eradication from 62.5% to 83.3% in 120 patients ^{21Reference 21Hajiaghamohammadi AA et al. · 2016RCTEffect of adding licorice to the standard treatment regimen of Helicobacter pylori — randomisedView study →}. In a second trial of 60 patients, licorice used in place of bismuth gave similar eradication rates ^{22Reference 22Momeni A et al. · 2014RCTEffect of licorice versus bismuth on eradication of Helicobacter pylori in peptic ulcer disease — randomisedView study →}. In the laboratory, licorice polysaccharides block H. pylori from attaching to stomach tissue ^{23Reference 23Wittschier N et al. · 2009In vitroAqueous extracts and polysaccharides from liquorice roots inhibit adhesion of Helicobacter pylori to human gastric mucosa — in vitroView study →}.

Gap: the DGL trials predate modern trial methods and proton-pump inhibitors.

Three randomised trials have tested topical licorice for radiotherapy-induced mouth sores in head-and-neck cancer. In 60 patients, a licorice mucoadhesive film reduced pain and mucositis severity at weeks 3 and 4 compared with placebo ^{28Reference 28Pakravan F et al. · 2021RCTEffect of Licorice Muco-adhesive Film on Radiotherapy-Induced Oral Mucositis — randomised controlled trialView study →}.

In another 60 patients, a licorice film was compared with a triamcinolone (corticosteroid) film for pain and ulceration ^{29Reference 29Ghalayani P et al. · 2017RCTTriamcinolone acetonide vs licorice mucoadhesive film on radiotherapy-induced oral mucositis: a randomised double-blinded clinical trialView study →}. In 37 patients, an aqueous Glycyrrhiza extract used from the start of radiotherapy was tested for prevention ^{30Reference 30Najafi S et al. · 2017RCTPreventive Effect of Glycyrrhiza glabra Extract on Oral Mucositis in Head-and-Neck Radiotherapy: a randomised clinical trialView study →}.

The effect is attributed to local anti-inflammatory and demulcent activity.

Gap: small single-centre trials with different formulations, and no large multicentre confirmation. This is supportive care only.

Licochalcone B specifically inhibits the NLRP3 inflammasome by disrupting the NEK7–NLRP3 interaction ^{24Reference 24Li Q et al. · 2022In vitroLicochalcone B specifically inhibits the NLRP3 inflammasome by disrupting NEK7-NLRP3 interaction — in vitroView study →}.

Licorice triterpenoids and flavonoids downregulate NF-κB and COX-2 signalling and protect the intestinal barrier in colitis models ^{25Reference 25Leite CDS et al. · 2022ReviewAnti-Inflammatory Properties of Licorice-Derived Compounds in Intestinal Disorders — reviewView study →}. Reviews of the licochalcones catalogue anti-inflammatory effects across cell and animal systems ^{26Reference 26Maria Pia GD et al. · 2019ReviewBiological Effects of Licochalcones — reviewView study →}.

In people, the anti-inflammatory action shows up indirectly, through the ulcer, mucositis and sore-throat trials, rather than through systemic inflammation markers.

Gap: most direct data are from cells or animals, and no trial has used a systemic marker such as CRP as its main outcome.

Two systematic reviews concluded that licorice preparations such as lollipops, rinses and toothpastes reduce salivary Streptococcus mutans and may help prevent caries in children ^{31,32Reference 31Tharakan AP et al. · 2020Systematic reviewEffectiveness of licorice in preventing dental caries in children: a systematic reviewView study →Reference 32Nuvvula S et al. · 2020Systematic reviewEfficacy of Licorice Lollipops in Reducing Dental Caries in a Paediatric Population: a systematic reviewView study →}.

In a randomised trial of 52 high-caries-risk patients, a licorice mouthwash lowered S. mutans as well as chlorhexidine did, although chlorhexidine gave a better plaque score ^{33Reference 33Helmy N et al. · 2021RCTEfficacy of Licorice on Salivary Streptococcus mutans vs Chlorhexidine Mouthwash in High Caries Risk Patients: a randomised clinical trialView study →}. In preschool children, two lollipops a day containing G. uralensis extract with glycyrrhizol A for 3 weeks reduced S. mutans while preserving overall oral microbial diversity ^{34Reference 34Chen Y et al. · 2019Clinical trialLollipop containing Glycyrrhiza uralensis extract reduces Streptococcus mutans colonization and maintains oral microbial diversity in Chinese preschool children — clinical trialView study →}.

A review of oro-dental uses also catalogues activity against periodontal and Candida organisms ^{35Reference 35Messier C et al. · 2012ReviewLicorice and its potential beneficial effects in common oro-dental diseases — reviewView study →}.

Gap: the outcome is usually the bacterial count, not caries over time, and trials are short and small.

Licorice lowers serum testosterone in people. Armanini’s group reported a fall in healthy men ^{36Reference 36Armanini D et al. · 1999Clinical trialReduction of serum testosterone in men by licorice — clinical trialView study →}, reproduced it in a larger group (a 26% fall after one week) ^{37Reference 37Armanini D et al. · 2003Clinical trialLicorice consumption and serum testosterone in healthy man — clinical trialView study →}, and found the same in healthy women taking 3.5 g of a preparation with 7.6% glycyrrhizic acid ^{38Reference 38Armanini D et al. · 2004Clinical trialLicorice reduces serum testosterone in healthy women — clinical trialView study →}.

In polycystic ovary syndrome, adding licorice to spironolactone reduced spironolactone’s volume-depletion symptoms ^{40Reference 40Armanini D et al. · 2007Clinical trialTreatment of polycystic ovary syndrome with spironolactone plus licorice — clinical trialView study →}. A 2024 double-blind RCT in 66 overweight women found 1.5 g/day of licorice extract with a low-calorie diet improved weight, body fat, blood sugar and lipids more than diet alone ^{41Reference 41Hooshmandi H et al. · 2024RCTEffects of licorice extract with a low-calorie diet on obesity, glycemic and lipid indices in overweight/obese women with PCOS: a randomised, double-blind, placebo-controlled trialView study →}.

A study of 100 g of liquorice a day (150 mg glycyrrhetinic acid) for four weeks found no significant change in testosterone ^{39Reference 39Sigurjonsdottir HA et al. · 2006Clinical trialLiquorice in moderate doses does not affect sex steroid hormones of biological importance — clinical trialView study →}.

Gap: the testosterone studies are small and short, the PCOS trials are few, and a meaningful glycyrrhizin dose also raises blood pressure.

In a randomised, double-blind, placebo-controlled study, GutGard (a G. glabra extract, 75 mg twice daily for 30 days) reduced functional-dyspepsia symptoms and improved quality of life ^{27Reference 27Raveendra KR et al. · 2012RCTAn Extract of Glycyrrhiza glabra (GutGard) Alleviates Symptoms of Functional Dyspepsia: a randomised, double-blind, placebo-controlled studyView study →}. The extract is standardised to a low glycyrrhizin content.

Gap: a single manufacturer-linked RCT that needs independent replication.

The human metabolic data come from licorice flavonoid oil (LFO), a fraction rich in glabridin dissolved in medium-chain triglycerides, not from ordinary root.

A single 600 mg dose of LFO increased fat oxidation during light exercise ^{45Reference 45Mori N et al. · 2015RCTEnhancement of Fat Oxidation by Licorice Flavonoid Oil in Healthy Humans during Light Exercise — randomisedView study →}. In older adults in knee-osteoarthritis rehabilitation, 300 mg/day for 16 weeks increased trunk muscle mass by 0.38 kg ^{46Reference 46Kinoshita T et al. · 2017RCTEffects of licorice flavonoid oil on increasing muscle mass: a randomised, double-blind, placebo-controlled trialView study →}.

⚠ Two eight-week placebo-controlled studies, in overweight adults and in overfed athletic men, found no significant effect on any measure ^{44Reference 44Bell ZW et al. · 2011Clinical trialEffect of dietary supplementation with licorice flavonoid oil on anthropometric and biochemical markers of health and adiposity — clinical trialView study →}.

Applied to the skin, a 2.5% glycyrrhetinic acid cream reduced the thickness of thigh fat in 18 women over one month ^{47Reference 47Armanini D et al. · 2005Clinical trialGlycyrrhetinic acid can reduce the thickness of subcutaneous thigh fat through topical application — clinical trialView study →}. In high-fat-fed rats, glycyrrhizic acid improved insulin sensitivity and lipoprotein-lipase expression ^{48Reference 48Eu CH et al. · 2010AnimalGlycyrrhizic acid improved lipoprotein lipase expression, insulin sensitivity and lipid deposition in high-fat-diet obese rats — animal modelView study →}.

Gap: the human benefits are for LFO, a proprietary oil, and do not transfer to licorice tea, powder or tincture.

Glycyrrhizin was among the most active compounds against the SARS coronavirus in a 2003 laboratory screen ^{49Reference 49Cinatl J et al. · 2003In vitroGlycyrrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus — in vitroView study →}.

Glycyrrhizin also inhibits SARS-CoV-2 replication by blocking the viral main protease in cell culture ^{50Reference 50van de Sand L et al. · 2021In vitroGlycyrrhizin Effectively Inhibits SARS-CoV-2 Replication by Inhibiting the Viral Main Protease — in vitroView study →}, and semi-synthetic glycyrrhizic-acid derivatives are more potent than the parent compound ^{51Reference 51Hoever G et al. · 2005In vitroAntiviral activity of glycyrrhizic acid derivatives against SARS-coronavirus — in vitroView study →}.

A systematic review of glycyrrhizin preparations in the SARS and MERS epidemics found supportive but low-quality clinical evidence ^{52Reference 52Li H et al. · 2020Systematic reviewThe Potential of Glycyrrhizinate in the Management of COVID-19: a systematic review of glycyrrhizin preparations in SARS and MERSView study →}.

Gap: the direct antiviral data are from cells or computer models, there is no controlled trial of oral licorice for an acute viral infection, and effective concentrations may not be reachable by mouth.

Glycyrrhizin’s metabolites inhibit 11β-hydroxysteroid dehydrogenase type 2, the enzyme that inactivates cortisol to cortisone in the kidney. Cortisol then acts on the mineralocorticoid receptor, which causes the apparent mineralocorticoid excess seen with high intake ^{56,62Reference 56Whorwood CB et al. · 1993AnimalLicorice inhibits 11β-hydroxysteroid dehydrogenase mRNA levels and potentiates glucocorticoid hormone action — animal modelView study →Reference 62Caré W et al. · 2023ReviewAdverse effects of licorice consumed as food: an update — reviewView study →}.

Herbalists use this cortisol-sparing action as an adrenal tonic and to help taper corticosteroid drugs.

Gap: “adrenal fatigue” is not a recognised diagnosis and has never been a trial outcome for licorice. The mechanism invoked is the same one that causes hypertension and low potassium.

Glabridin and other licorice flavonoids scavenge free radicals in laboratory systems ^{43,68Reference 43Asl MN et al. · 2008ReviewReview of pharmacological effects of Glycyrrhiza sp. and its bioactive compounds — reviewView study →Reference 68Wahab S et al. · 2021ReviewGlycyrrhiza glabra (Licorice): a comprehensive review on its phytochemistry, biological activities, clinical evidence and toxicology — reviewView study →}. In the NAFLD trial in women, licorice lowered malondialdehyde, a marker of oxidative stress ^{7Reference 7Rostamizadeh P et al. · 2022RCTEffects of licorice root supplementation on liver enzymes, steatosis and oxidative stress in women with NAFLD: a randomised double-blind trialView study →}.

Gap: the evidence is mainly constituent-level laboratory work, and no trial has used an oxidative-stress panel as its main outcome.

In a randomised double-blind trial, 60 postmenopausal women took licorice (1,140 mg/day) or hormone replacement therapy for 90 days. Licorice reduced the number and duration of hot flushes about as much as HRT, but HRT reduced their severity significantly more ^{53Reference 53Menati L et al. · 2014RCTEvaluation of licorice effects on reducing hot flashes in postmenopausal women — randomisedView study →}.

The rationale is the phytoestrogenic isoflavonoids of the root, such as glabridin and formononetin.

Gap: a single small trial with no placebo arm.

Glabridin inhibits tyrosinase, the enzyme behind skin pigmentation, and licorice extract is widely used in cosmetics for this. Recent work identified the depigmenting components of G. glabra extract and the CRTC1/MITF pathway they inhibit ^{63Reference 63Liu J et al. · 2025In vitroGlycyrrhiza glabra extract as a skin-whitening agent: active components and CRTC1/MITF pathway inhibition — in vitroView study →}. A transdermal delivery system was engineered to carry poorly soluble glabridin across the skin ^{64Reference 64He J et al. · 2023In vitroTetrahedral framework nucleic acid loaded with glabridin: a transdermal delivery system for anti-hyperpigmentation — in vitroView study →}.

In animal work, glabridin reduced atopic dermatitis through TLR4/NF-κB downregulation ^{65Reference 65Chang J et al. · 2021AnimalGlabridin attenuates atopic dermatitis progression via TLR4/MyD88/NF-κB downregulation — animal modelView study →}.

Gap: the evidence is laboratory and delivery-focused, and there are no controlled clinical depigmentation trials of a defined licorice product.

Licorice isoflavans and isoflavenes, chiefly glabridin, inhibited serotonin reuptake in the laboratory in a dose-dependent way, while the isoflavones genistein and daidzein were largely inactive ^{54Reference 54Ofir R et al. · 2003In vitroInhibition of serotonin re-uptake by licorice constituents — in vitroView study →}.

In a high-throughput screen, glycyrrhisoflavone and the coumarin licocoumarone inhibited human MAO-B ^{55Reference 55Mazzio E et al. · 2013In vitroHigh throughput screening to identify natural human monoamine oxidase B inhibitors — in vitroView study →}.

Gap: these are laboratory findings with no animal behavioural model and no human trial.

A licorice-root polyphenol induced apoptosis, G2/M cell-cycle arrest and Bcl-2 phosphorylation in tumour cell lines ^{67Reference 67Rafi MM et al. · 2002In vitroNovel polyphenol molecule from licorice root induces apoptosis, G2/M arrest and Bcl-2 phosphorylation in tumor cell lines — in vitroView study →}. Reviews of the licochalcones describe effects on EGFR/ERK, PI3K/Akt/mTOR, apoptosis and angiogenesis across many cancer models ^{66Reference 66Deng N et al. · 2023ReviewAnticancer effects of licochalcones: a review of the mechanisms — reviewView study →}.

Gap: laboratory work only, with no human data.

How the harm happens. Glycyrrhizin’s metabolites block 11β-hydroxysteroid dehydrogenase type 2 in the kidney, so cortisol acts as a mineralocorticoid ^{62Reference 62Caré W et al. · 2023ReviewAdverse effects of licorice consumed as food: an update — reviewView study →}. The result is a dose- and duration-dependent pseudo-aldosteronism: sodium and water retention, raised blood pressure, potassium loss and suppression of renin and aldosterone ^{57,62Reference 57Penninkilampi R et al. · 2017Meta-analysisThe association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysisView study →Reference 62Caré W et al. · 2023ReviewAdverse effects of licorice consumed as food: an update — reviewView study →}.

The size of the effect. A meta-analysis of 18 studies (337 people) taking at least 100 mg of glycyrrhizic acid a day found systolic pressure rose by 5.45 mmHg, diastolic by 3.19 mmHg, and potassium fell by 0.33 mmol/L. Blood pressure rose with the daily dose ^{57Reference 57Penninkilampi R et al. · 2017Meta-analysisThe association between consistent licorice ingestion, hypertension and hypokalaemia: a systematic review and meta-analysisView study →}.

Serious cases. Case reports describe severe hypertension, very low potassium, oedema, muscle weakness, paralysis, rhabdomyolysis and heart-rhythm disturbances with chronic or high intake ^{58,60Reference 58Ceccuzzi G et al. · 2023ReviewLiquorice Toxicity: A Comprehensive Narrative ReviewView study →Reference 60Awad N et al. · 2020Case reportLicorice-induced apparent mineralocorticoid excess causing persistent hypertension and hypokalemia — case reportView study →}. The EMA lists water retention, low potassium, high blood pressure, heart-rhythm disorders and hypertensive encephalopathy after use beyond 4 weeks or at high amounts ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

A daily ceiling. The EU Scientific Committee on Food set an upper limit of 100 mg of glycyrrhizic acid a day for regular intake, about the amount in 60 g of licorice confectionery ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}. It noted that this limit may not protect people with high blood pressure, electrolyte or fluid-balance conditions, slow gut transit, or reduced 11β-HSD2 activity ^{75Reference 75Committee on Herbal Medicinal Products · 2026ReviewAssessment report on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory reviewView study →}.

Health conditions. The EMA does not recommend licorice medicines for people with high blood pressure, kidney disease, liver or cardiovascular disorders, or low potassium, because they are more sensitive to these effects ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

Drug interactions. Licorice may counteract blood-pressure medication ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}. It should not be combined with diuretics, cardiac glycosides such as digoxin, corticosteroids, stimulant laxatives or other drugs that can upset electrolyte balance ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

Glycyrrhizin at 300 mg/day for 14 days modestly lowered blood levels of midazolam and omeprazole, drugs broken down by the CYP3A4 enzyme, so caution is advised with any drug handled by that enzyme ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

Duration and other licorice products. For indigestion the EMA limits use to 4 weeks, and people taking a licorice medicine should not also take other licorice-containing products ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

Children. Not recommended under 18 ^{74Reference 74Committee on Herbal Medicinal Products · 2026ReviewEuropean Union herbal monograph on Glycyrrhiza glabra L.; Glycyrrhiza inflata Bat.; Glycyrrhiza uralensis Fisch., radix, final — revision 1 — regulatory monographView study →}.

Testosterone. Licorice lowers serum testosterone in both men and women ^{37,38Reference 37Armanini D et al. · 2003Clinical trialLicorice consumption and serum testosterone in healthy man — clinical trialView study →Reference 38Armanini D et al. · 2004Clinical trialLicorice reduces serum testosterone in healthy women — clinical trialView study →}.

DGL. Deglycyrrhizinated licorice removes most of the glycyrrhizin and with it most of this risk, but also part of the activity.