Liquorice is substantiated for cosmetic use for a range of skin care needs, as an anti-inflammatory product with benefits for skin sensitivity, hyperpigmentation and concerns such as eczema and acne. Chinese ingredient maker BGG reviews the scientific evidence for the benefits of liquorice extracts from a skin care perspective, with a focus on the bioactive compounds glycyrrhizin, glabridin and licochalcone.

With sustainability, eco-awareness and naturality now cemented as mainstream consumer concerns worldwide, demand for plant-based ingredients is rising. The global beauty and personal care (BPC) market is no exception, with consumers demonstrating a growing preference for natural solutions. NielsenIQ market research, for example, shows that 18% of all BPC sales feature products incorporating botanic extracts.¹

Liquorice fits this trend as a clinically supported botanical ingredient. The herbaceous perennial has been a mainstay of traditional medicine systems for thousands of years for its antioxidant, anti-inflammatory and antibacterial properties.² Today, these attributes and its positioning as a natural, sustainable ingredient are leading to liquorice’s increasing incorporation in modern skin care products.

This article reviews the scientific evidence for the benefits of liquorice extracts from a skin care perspective, with a focus on the bioactive compounds glycyrrhizin, glabridin and licochalcone A and their use for specific skin conditions. These include hyperpigmentation, sun-ageing, eczema, rosacea, skin sensitivity, acne and subcutaneous fat reduction.

Liquorice active constituents and properties

Classed as an essential herbal medication and the most frequently prescribed ingredient in traditional Chinese medicine, liquorice (genus Glycyrrhiza) is native to western Asia, southern Europe and north Africa. The three most commonly used species are G. glabra L., G. inflata Batalin and G. uralensis Fisch. Their thick roots and rhizomes are rich in bioactive natural compounds, many of which have demonstrated efficacy as cosmeceutical ingredients.³

Over 400 phytochemicals have been identified in liquorice, including saponins, flavonoids, volatile compounds, phenolic compounds and essential oils.⁴ The primary active in the root is the triterpenoid saponin glycyrrhizin (also known as glycyrrhizic acid), a mixture of potassium, calcium and magnesium salts of glycyrrhizic acid.²

It accounts for around 10% of the root’s dry weight and is responsible for liquorice’s characteristic sweet flavour.² Glycyrrhizin is associated with strong anti-inflammatory and skin-soothing properties.5 Its primary metabolite is 18ß-glycyrrhetinic acid (also known as enoxolone), which has been extensively studied for its anti-inflammatory properties.⁶

Glabridin is the primary isoflavone in liquorice and has been shown to inhibit melanin production and pigmentation and brighten skin tone.^7,8 Licochalcone A is a liquorice flavonoid found primarily in G. inflata.⁹ It has antibacterial and anti-inflammatory properties, with demonstrated efficacy for acne and dermatitis.^9,10 The structures of these selected compounds are shown in Figure 1.

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Overview of mechanisms of action

Glycyrrhizin and 18ß-glycyrrhetinic acid have been shown to reduce inflammation by acting on a number of immune-signalling pathways, including three pro-inflammatory pathways — NFx-χb, TLR4/MYD88 and MAPK — and the anti-inflammatory Keap1-Nrf2 pathway.⁴ Their anti-inflammatory activities include inhibition of pro-inflammatory compounds such as cytokine COX-2, inducible nitric oxide synthase (iNOS), tumour necrosis factor and interleukin 6 (IL-6).¹¹

Glabridin is known to suppress the release of nitric oxide (NO), a free radical that can be pro-inflammatory when overproduced, and interleukin factor 1ß (IL-1ß), a potent pro-inflammatory cytokine.¹¹ It has also been shown to inhibit the pro-inflammatory prostaglandin E2 (PGE2) and the activity of the pro-inflammatory NF-χb and MAPK signalling pathways.¹² In addition, glabridin inhibits tyrosine, an enzyme that plays a key role in melanin production and skin pigmentation.^2,3

Licochalcone A inhibits synthesis of NO, IL-6 and reactive oxygen species (ROS) and reduces serum levels of immunoglobulin E and G, which are involved in allergic reactions.¹¹ It also inhibits the pro-inflammatory NF-χb pathway and activates the anti-inflammatory Keap1-Nrf2 pathway (Figure 2).⁴ Like glabradin, licochalcone A inhibits tyrosine, and additionally suppresses the activity of the pro-inflammatory NLRP3 inflammasome.^2,10

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Clinically supported skin benefits: Hyperpigmentation, skin brightening and photo-ageing

One of the skin’s key roles is to safeguard the body from the harmful effects of exposure to ultraviolet (UV) radiation. UV irradiation accelerates the production of melanin, which absorbs the UV radiation to protect skin cells and creates a tan that acts as a natural sunscreen. However, chronic UV exposure can lead to erythema (redness), photo-ageing (by damaging connective tissue in the dermis, causing wrinkles) and hyperpigmentation (including freckles and age spots, also known as solar lentigines) (Figure 3).

Liquorice has traditionally been used as a skin-brightening agent. Tyrosinase is an enzyme that mediates the initial steps in melanin production, with tyrosinase inhibitors widely used in cosmetic applications such as skin-brightening agents.¹³

Several liquorice extracts have been shown to act as tyrosinase inhibitors, thereby reducing the risk of hyperpigmentation.⁶ This was first demonstrated in 1998 in an in vitro study, which found that UVB-induced pigmentation and erythema in guinea pig skin were inhibited by topical application of 0.5% glabridin.⁷

In a clinical study comparing the effects of topically applied glycyrrhetinic acid and CO2 fractional laser therapy on hand solar lentigines, 11 participants were split into two groups. One group received laser treatment followed by four weeks of the topical treatment with laser, and the other group underwent topical treatment only. After four weeks, all participants experienced improvements in the lentigines, with no statistical differences between the two groups.¹⁴

Licochalcone A has also been found to demonstrate photo-protective properties. A double-blind, placebo-controlled clinical trial randomised 22 participants to application of either licochalcone A extract or a placebo on their forearms twice a day for four weeks. The test areas were then irradiated with UVA, with skin luminescence measured by ultra-weak photon emission detection. The licochalcone A group showed significantly lower levels of UVA-induced luminescence, indicating a reduction in oxidative processes.¹⁵

Eczema

Atopic dermatitis is the most common type of eczema, characterised by inflammation, skin dryness and cracking, and itching severe enough to disturb sleep. Common topical treatments, including corticosteroids, antimicrobials and immunomodulators, can cause adverse effects, particularly with long-term use. This has led to emerging interest in herbal-based products, including liquorice extracts, as efficacious alternatives with fewer side effects.

The anti-inflammatory effects of glycyrrhetinic acid for the safe and effective treatment of mild to moderate atopic dermatitis have been demonstrated in a multi-centre, randomised phase IV trial.¹⁶

For five weeks, 218 adults with atopic dermatitis self-administered either a 2% hydrophilic ointment with 2% glycyrrhetinic acid or a placebo cream three times a day to affected areas and areas prone to being affected. Those using the glycyrrhetinic acid cream experienced a statistically significant 80% improvement in symptoms compared to 10% using the placebo.

In a clinical randomised pilot study, participants with atopic dermatitis applied a topical cream with 0.6% glycyrrhizinic acid and 0.1% G. uralensis root extract twice daily. After two weeks, the cream significantly reduced inflammation compared to placebo and demonstrated the same efficacy for inflammation reduction as 1% hydrocortisone acetate, with no side effects.¹⁷

Licochalcone A has also shown efficacy for atopic dermatitis. A randomised pilot study compared a moisturiser containing licochalcone A with hydrocortisone lotion for the treatment of mild to moderate atopic dermatitis in children. After six weeks of twice-daily application, the licochalcone cream was as effective as the hydrocortisone lotion.¹⁸

A 12-week, double-blind, randomised control trial showed that an emollient containing licochalcone A prevented flares in adults with mild to moderate atopic dermatitis.⁹ There was a significant reduction in the number of relapses in areas treated with the active formulation compared to placebo. Furthermore, itch severity was also significantly less pronounced during relapse in the active-treated areas compared to placebo.

Contact dermatitis is a type of eczema caused by the skin coming into contact with irritants and allergens, manifesting as an itchy rash. A recent study evaluated a gel with 8% G. glabra root as the active ingredient for the treatment of inflammatory skin conditions, and contact dermatitis in particular. The gel demonstrated anti-inflammatory, free-radical scavenging (antioxidant) and antibacterial effects, with the researchers highlighting its potential for reducing the symptoms of dermatitis.⁵

Rosacea and sensitive skin

Rosacea is a common inflammatory skin condition, with symptoms including persistent erythema, flushing, visible blood vessels, solid red bumps and pus-filled pimples that can resemble acne. Sufferers are often sensitive to skin care products, which may aggravate irritation and inflammation.

In an eight-week clinical trial, 62 patients with mild to moderate facial erythema used a skin care regimen containing licochalcone A. Clinical assessments and a quality-of-life questionnaire were conducted at baseline and at the end of the trial. The licochalcone treatment significantly reduced facial redness and was well tolerated.¹⁹ In a later randomised, prospective study, licochalcone A demonstrated a statistically significant improvement in erythema control and skin hydration for symptom reduction after four weeks.²⁰

Licochalcone A has also demonstrated effectiveness in the treatment of sensitive skin, a condition affecting over 50% of adults. It is characterised by inflammation, erythema, pruritus (severe itching) and prickling or burning sensations. In an in vitro study, licochalcone A significantly decreased NF-χb signalling and the secretion of PGE2. The researchers then conducted two controlled, single-blinded, randomised clinical trials, which found that a post-shaving cream combining licochalcone A with 4-t-butycyclohexanol (an emollient agent known for its skin-soothing properties) reduced shaving-induced erythema.²¹

Acne

Acne vulgaris is one of the most common skin diseases, often occurring during puberty but also presenting as an adult-onset condition. Propionibacterium acnes (recently reclassified as Cutibacterium acnes) is a commensal skin bacterium implicated in the development of acne by stimulating the NLRP3 inflammasome, which plays a crucial role in inflammatory signalling. Licochalcone A has been demonstrated to control skin inflammation induced by P. acnes by suppressing NLRP3 inflammasome activity.¹⁰

Subcutaneous fat reduction

Fat distribution and deposition are modulated by the catabolic hormone cortisol, which is converted from the inactive cortisone form by the enzyme 11ß-hydroxysteroid dehydrogenase type 1. Glycyrrhetinic acid blocks the enzyme, thereby decreasing cortisol available to adipocytes and inhibiting their growth.

In a double-blind clinical study, ¹⁸ women were randomly assigned to apply either 2.5% glycyrrhetinic acid or a placebo cream on the thigh. Circumference and ultrasound measurements of superficial fat layer thickness were taken at baseline and one month after twice daily application. Significant reductions in circumference and superficial fat layer thickness were observed in the treatment group compared to both the untreated thigh and the placebo group.²²

Liquorice quality control and sustainability

The growing popularity of and demand for traditional herbal medicines such as liquorice brings increasing challenges around adulteration. In the United States, it has been estimated that up to 50% of products may include incorrect species.²³ This has implications for product efficacy as well as consumer health and confidence in herbal products.

The UK Centre for the Promotion of Imports (CBI) recommends that liquorice buyers adopt quality management standards such as ISO 2200 and ISO 9001:2015 by the International Organization for Standardization and Food Safety System Certification (FSSC) 2200. Countries including the United States, UK, China, Japan and Thailand have also strengthened regulatory oversight of natural herbal remedies. Methods for identifying plant species include DNA analysis and barcoding.²³

The sustainability of herbal products is another growing consumer concern. NielsenIQ’s 2023 Sustainable Beauty report found that 62% of consumers now view sustainability as a greater priority compared to two years ago,²⁴ yet accelerating demand has endangered wild liquorice species in recent years.²³

BGG has been extracting liquorice roots since 1995 and controls the entire supply chain, from harvesting to the finished product. Its liquorice roots are sourced from wildcrafted plants in pristine regions across Asia and the Middle East, including China, Azerbaijan, Kazakhstan, Turkmenistan, Tajikistan and Uzbekistan.

To ensure sustainability, the roots are harvested in winter from three- to four-year-old plants after their leaves have fallen. This method helps preserve the plants for future growth. Once collected, the roots undergo botanical identification, cleaning and drying. They are then quarantined and subjected to comprehensive chemical screening for contaminants. Any batch failing a single test is discarded.

Each liquorice product uses a specific liquorice species and the manufacturing process is tightly regulated, from grinding and extraction to concentration, purification, drying, packaging and labelling. All materials are certified non-GMO by independent third-party auditors such as Ecocert.

Conclusion

Research from Euromonitor International shows that skin treatments and moisturisers accounted for almost 25% of new product development in the BPC space in 2023, with innovation centred on wellness and efficacy benefits.²⁵

Liquorice is substantiated for cosmetic use by traditional knowledge and modern science, demonstrating its versatility for a range of skin care needs, including as an anti-inflammatory product with benefits for skin sensitivity, hyperpigmentation and concerns such as eczema and acne. In a market increasingly focused on natural, plant-based, sustainably sourced ingredients, liquorice is an effective solution for advanced skin care products targeting naturally healthy skin.

References

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