It is a herbaceous perennial, growing to 1 m in height, with pinnate leaves about 7–15 centimetres (3–6 in) long, with 9–17 leaflets. The flowers are 0.8–1.2 cm (½–⅓ in) long, purple to pale whitish blue, produced in a loose inflorescence. The fruit is an oblong pod, 2–3 centimetres (1 in) long, containing several seeds. The roots are stoloniferous. The flavor of liquorice comes mainly from a sweet-tasting compound called anethole ("trans"-1-methoxy-4-(prop-1-enyl)benzene), an aromatic, unsaturated ether compound also found in anise, fennel, and several other herbs. Much of the sweetness in liquorice comes from glycyrrhizin, a compound sweeter than sugar.

The compound glycyrrhizic acid, found in liquorice, is now routinely used throughout Japan for the treatment and control of chronic viral hepatitis, and there is a possible transaminase-lowering effect.^[14] Hepatoprotective mechanisms have been demonstrated in mice.^[15] Recent studies indicate that glycyrrhizic acid disrupts latent Kaposi sarcoma (as also demonstrated with other herpesvirus infections in the active stage), exhibiting a strong anti-viral effect.^[16] The Chinese use liquorice to treat Tuberculosis ^[17]

Liquorice affects the body's endocrine system as it contains isoflavones (phytoestrogens). It might lower the amount of serum testosterone slightly,^[18] but whether it affects the amount of free testosterone is unclear. Consuming liquorice may prevent the development of hyperkalemia in persons on hemodialysis.^[19] Large doses of glycyrrhizinic acid and glycyrrhetinic acid in liquorice extract can lead to hypokalemia and serious increases in blood pressure, a syndrome known as apparent mineralocorticoid excess. These side effects stem from the inhibition of the enzyme 11β-hydroxysteroid dehydrogenase (type 2) and subsequent increase in activity of cortisol on the kidney. 11β-hydroxysteroid dehydrogenase normally inactivates cortisol in the kidney; thus, liquorice's inhibition of this enzyme makes the concentration of cortisol appear to increase. Cortisol acts at the same receptor as the hormone aldosterone in the kidney and the effects mimic aldosterone excess, although aldosterone remains low or normal during liquorice overdose. To decrease the chances of these serious side effects, deglycyrrhizinated liquorice preparations are available. The disabling of similar enzymes in the gut by glycyrrhizinic acid and glycyrrhetinic acid also causes increased mucus and decreased acid secretion. As it inhibits Helicobacter pylori, is used as an aid for healing stomach and duodenal ulcers, and in moderate amounts may soothe an upset stomach. Liquorice can be used to treat ileitis, leaky gut syndrome, irritable bowel syndrome and Crohn's disease as it is antispasmodic in the bowels.^[20]

Studies of the use of liquorice extract (usually at 7%) in the treatment of melasma have shown that glabridin inhibits tyrosinase activity of melanocytes. ^[21]

The compounded carbenoxolone is derived from liquorice. Some studies indicate that it inhibits 11β-Hydroxysteroid dehydrogenase type 1, an enzyme that is highly expressed in liver and fat tissues, where it plays a role in metabolism, and in the brain, where the same enzyme is involved in stress response that has been associated with age-related mental decline.^[22][23]

Alternative medicine

In traditional Chinese medicine, liquorice(甘草) is commonly used in herbal formulae to "harmonize" the other ingredients in the formula and to carry the formula to the twelve "regular meridians"^[24] and to relieve a spasmodic cough.

In herbalism it is used in the Hoxsey anti-cancer formula, and is a considered adaptogen which helps reregulate the hypothalamic-pituitary-adrenal axis. It can also be used for auto-immune conditions including lupus, scleroderma, rheumatoid arthritis and animal dander allergies.^[20]

Glycyrrhizin from Glycyrrhiza root has been shown to modulate airway constriction, lung inflammation and infiltration of eosinophils in bronchial areas by stimulating CD4 and CD8 immune cell function.^[25]

Liquorice may be useful in conventional and naturopathic medicine for both mouth ulcers^[26] and peptic ulcers.^[27]