Vol. 38, Issue 3, Page 24 (March 2007)

LESLIE S. BAUMANN, M.D.

DR. BAUMANN is director of cosmetic dermatology at the University of Miami. To respond to this column, or to suggest topics for future columns, write to Dr. Baumann at our editorial offices via e-mail at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Licorice (Glycyrrhiza glabra L., also known as Liquiritae officinalis Moench) is best known in its popular confectionery form—a black or red candy sold at movies and various retail establishments. It is not often thought of as a plant, let alone a botanical source of systemic or topical medication.

The fact remains, though, that licorice, or licorice root, is believed to have been used in herbal medicine for 4,000 years (Lloydia 1978;41:348–54).

It also is one of the oldest and most popular herbs in traditional Chinese medicine, where it is second only to ginseng (Nutr. Cancer 2001;39:1–11).

G. glabra is a perennial herb that originated around the Mediterranean Sea, the Middle East, and central and southern Russia (Nutr. Cancer 1991;15:187–93).

It is now cultivated in much of Asia, Europe, and the Middle East, and is used globally as a pharmacologic agent, particularly in anti-inflammatory products (Phytother. Res. 2003;17:987–1000; Cosmet. Toiletries 1997;112:57–64).

Licorice root is also believed to possess antiviral, antiulcer, and anticarcinogenic properties (Nutr. Cancer 2001;39:1–11).

In China, it has served as a folk elixir and antidote, and has long been used as a demulcent (Nutr. Cancer 1991;15:187–93).

G. glabra has been used in a broad range of medical indications. Regarding cutaneous indications, the extract has been used to treat dermatitis, eczema, pruritus, cysts, and skin irritation (J. Dermatolog. Treat. 2003;14:153–7; Agro Food Industry Hi-Tech. 1997;8:28–31).

In the modern pharmacopoeia, licorice is incorporated into cosmetics for acne patients and the treatment of sunburn (Agro Food Industry Hi-Tech. 1997;8:28–31).

Active Components

Glycyrrhizin, the primary water-soluble constituent of licorice, has been shown to confer many pharmacologic benefits, although various derivatives also possess these properties (Nutr. Cancer 1991;15:187–93).

Glycyrrhizin is a sweet-tasting triterpene saponin that exhibits poor blood solubility, compared with other saponins.

It is typically present in the root in 5%–10% concentrations, and is the source of the plant's sweetness (Phytother. Res. 2003;17:987–1000; Skin Ther. Lett. 2000;5[4]:3–5; Integr. Cancer Ther. 2003;2:120–38).

In addition to glycyrrhizin and its aglycone form glycyrrhizic acid, licorice root contains polysaccharides and various polyphenols, such as the isoflavone formononetin (Nutr. Cancer 2001;39:1–11), to which antioxidant properties are ascribed.

The antiulcer capacity of licorice root is attributed primarily to glycyrrhetic acid (Lancet 1991;337:428–9; Irish Med. J. 1985;78:153–6), which is the biologically active metabolite of glycyrrhizic acid (Drug Metab. Rev. 2001;33:125–47; Skin Ther. Lett. 2000;5[4]:3–5). Its long history of traditional use and track record of positive research in the past few decades make licorice one of the most widely researched plants for medicinal purposes.

Anti-Inflammatory Action

Earlier research on licorice extract reportedly showed that topical ointments containing active isomers of glycyrrhetic acid had anti-inflammatory activity in subacute and chronic dermatoses, such as contact dermatitis, seborrheic dermatitis, and psoriasis.

Topical corticosteroids were more effective than glycyrrhetic acid formulations in treating acute atopic dermatitis (Br. J. Clin. Pract. 1958;12:269–74).

But glycyrrhetic acid has been characterized as exerting a cortisonelike effect, rendering it a viable anti-inflammatory agent, and it has been shown to inhibit proinflammatory prostaglandins and leukotrienes (Acta Med. Okayama 1983;37:385–91; Prostaglandins Med. 1981;7:457–63).

Combining glycyrrhetic acid with corticosteroids also has been shown to be effective. In one study, results from topical corticosteroid application were significantly improved with the addition of 2% glycyrrhetic acid (Lancet 1990;335:1060–3).

More recently, glycyrrhetic acid has been used successfully to treat moderate inflammation without secondary infection (J. R. Soc. Health 1998;118:300–4).

In a double-blind study conducted over 2 weeks, investigators evaluated the effect of 1% and 2% topical licorice extract preparations on atopic dermatitis in two 30-patient groups. The results indicated that the 2% topical gel was more effective in reducing erythema, edema, and pruritus. Significantly, the authors also concluded that licorice extract was effective in treating atopic dermatitis (J. Dermatolog. Treat. 2003;14:153–7).

In a series of animal studies, Russian scientists found that glyderinine, a derivative of glycyrrhizic acid, exhibited anti-inflammatory effects and analgesic and antipyretic properties. The researchers concluded that glyderinine is an appropriate ingredient in ointments for the treatment of skin diseases (Farmakol. Toksikol. 1988;51[4]:90–3).

Glabridin, the main component in the hydrophobic fraction of licorice extract, has been found to inhibit inflammation and melanogenesis in cultured B16 murine melanoma cells and guinea pig skin (Pigment Cell Res. 1998;11:355–61).

Antitumor Action

Feeding licorice extract to SENCAR mice has been shown to protect against skin tumorigenesis caused by 7,12-dimethylbenz[a]anthracene initiation and 12-O-tetradecanoylphorbol-13-acetate promotion. Tumors developed much more quickly in mice not fed the licorice preparation, and treated mice had significantly fewer tumors during and at the end of the study.

The researchers concluded that the considerable antitumorigenic activity of licorice extract might ultimately be proved useful in protecting against some forms of human cancer (Nutr. Cancer 1991;15:187–93).

Since the time this study was published, the polyphenols in licorice have been shown to induce apoptosis in cancer cells, and licorice constituents have exhibited antimutagenic, anticarcinogenic, and tumor-suppressive capacity in animal models (Nutr. Cancer 2001;39:1–11).

In fact, the National Cancer Institute has formally recognized the chemopreventive worth of licorice root and its primary constituent, glycyrrhizin (Am. J. Clin. Nutr. 1999;70:491S–9S).

Bleaching Action

In a study of 20 women aged 18–40 years with a clinical diagnosis of bilateral and symmetrical idiopathic epidermal melasma, liquiritin cream was applied on one side of the face and a vehicle cream on the other twice daily for 4 weeks.

Liquiritin is a flavonoid in licorice that, along with other components, imparts the natural yellow color.

Patients with dermal melasma and melasma with pregnancy were excluded from the study, as were those receiving hormone therapy. Sun exposure was discouraged during the treatment period, and topical sunscreen use was encouraged.

In all, 16 patients (80%) were characterized as exhibiting excellent responses to liquiritin, with no discernible differences between the normal skin and previously pigmented areas.

Two patients (10%) showed a good response on the liquiritin side, and two patients (10%) had fair responses to liquiritin, with moderate pigmentation, whereas moderate improvement was seen in only 20% on the vehicle side (Int. J. Dermatol. 2000;39:299–301).

At the Store

Licorice is used in the United States more often as a flavoring and sweetener in foods than for salutary purposes (Nutr. Cancer 2001;39:1–11), although licorice candy is typically flavored with anise oil, not licorice.

The U.S. Food and Drug Administration bestowed Generally Recognized as Safe (GRAS) status on licorice in 1983 (Integr. Cancer Ther. 2003;2:120–38).

Several herbal product companies make licorice oral supplements and topical preparations that contain licorice extract amid a cocktail of other botanical ingredients.

Licorice extract is widely used as an anti-inflammatory in Europe and has been reported to be a successful antiviral medication for chronic hepatitis (Skin Ther. Lett. 2000;5[4]:3–5).

The use of oral licorice also is approved by the German Commission E for the treatment of bronchitis and chronic gastritis. Liquiritin cream, discussed above, has demonstrated efficacy in the treatment of melasma.

Neither this product nor other topical products containing licorice extract as the primary active ingredient are yet approved or available in the United States (Skin Ther. Lett. 2000[4];5:3–5).

In a study of prolonged licorice intake, researchers administered daily doses of licorice root extract containing graded amounts of glycyrrhizin to male and female volunteers for 4 weeks.

The rare side effects observed were dose-dependent and occurred more often in women and with the use of oral contraceptives (Life Sci. 1994;55:863–72).

Oral licorice is also contraindicated in people with hypertension and patients with cardiac or renal histories (Skin Ther. Lett. 2000;5[4]:3–5).

Conclusions

In addition to its long record of traditional use, licorice root has been evaluated in a broad range of modern scientific studies.

The reputed anti-inflammatory, antiviral, and anticarcinogenic properties of licorice root are particularly intriguing, especially because the body of supportive evidence is expanding.

The great challenge in producing cosmeceuticals—harnessing the identified strengths of a given ingredient and bottling it as a topical formulation to relay its health effects—applies here, as with most of the ingredients discussed in this column.

The wealth of evidence points to the benefits of the licorice plant, indicating that such benefits have been reaped in oral and topical preparations of the extract.

Given the wealth of history and research supporting its use, I expect to see licorice root incorporated into more products.

But more research is necessary before we can realistically accept this herb into the dermatologic armamentarium as a first-line therapy for the wide range of its potential uses.

Next month we will turn to the East, focusing more on G. glabra's Chinese cousin, G. inflata, and its wide-ranging pharmaceutical and dietary uses.

PII: S0037-6337(07)70130-4

doi:10.1016/S0037-6337(07)70130-4

© 2007 Elsevier Inc. All rights reserved.