If I mention liquorice to you, you probably think I’m talking about confectionery. I am originally from the Netherlands and it’s a well-known Dutch delicacy which you can buy in every supermarket and corner shop. However, did you know that liquorice is actually a wonderful skincare herb?
Liquorice or licorice (Glycyrrhiza glabra) is a leafy green plant which yields small purple to pale blue flowers. It also grows long tap roots which can extend down well over a metre and has horizontal rhizomes which spread out widely. It is these roots which yield the characteristic flavour we know as liquorice. The root is boiled down and the water evaporated in order to produce liquorice extract. Countries producing liquorice include Iran, Afghanistan, China, Pakistan, Iraq, Azerbaijan, Uzbekistan, Turkmenistan and Turkey.
Liquorice has been used for many thousands of years to treat skin ailments. Pliny said it could be used to treat wounds, as did the Greek scholar Theophrastus (287 BC) who recommended that it was mixed with honey to heal the skin. Liquorice has also been used successfully to treat stomach ulcers, control inflammation and help with coughs and sore throats.
Liquorice contains various cosmeceutical compounds, including glycyrrhizin, glabridin and liquiritin, to name but a few of its chemical constituents. Let’s have a look at what these compounds do when applied topically:
Liquorice in Skincare: Glycyrrhizin
Most of the sweetness in liquorice comes from glycyrrhizin (also known as glycyrrhizic acid), which has a sweet taste, 30–50 times the sweetness of sugar. Liquorice root contains approximately 2-9% glycyrrhizin.
Glycyrrhizin has been shown to have anti-inflammatory activity because it has been found to mimic cortisol in our bodies. Cortisol is a steroid hormone which is released in our body in response to stress. It regulates and reduces inflammation in the body, so by glycyrrhizin mimicking cortisol it is indirectly having an anti-inflammatory effect.
This has also been shown to be the case when liquorice is applied topically. In 2003 a clinical trial was undertaken to look at the effects of applying a liquorice gel to people with dermatitis (eczema). After two weeks, redness, swelling and itching had decreased significantly in the 100+ people studied as part of the trial. The study found that liquorice extract could be considered an effective herb for the treatment of eczema.
Glycyrrhizin has also been found to act as a penetration enhancer when it comes to topically applied drugs. A joint research team at King’s College London and Tabriz Medical Science University in Iran examined the use of glycyrrhizin in drugs applied to the skin. They found that glycyrrhizin was particularly successful at enhancing penetration of active ingredients into the skin when it was used in a gel, rather than a lotion or cream (i.e. an emulsion).
Liquorice in Skincare: Glabridin
Liquorice also contains a compound called glabridin which is a phytoestrogen. Phytoestrogens are plant derived compounds with biological activities comparable to the human hormone oestrogen. It is well known that oestrogen stimulates the body to make collagen and hyaluronic acid – two essential components of the skin which form an important part of the connective tissue and keep our skin looking young.
So a cosmetic product containing glabridin is thought to encourage the skin to create its own strengthening connective tissues. Studies have found that topical application of phytoestrogens were found to reduce the depth of wrinkles and increase general tone and hydration of the skin.
But glabridin does more than just providing anti-ageing properties! It is also inhibits the activity of an enzyme called tyrosinase which is known to be a key enzyme in determining the colour of our skin and hair. Some people suffer from discolouration of the skin – examples include age spots or hyperpigmentation. In fact, pigmentary disorders are the third most common dermatologic problem.
Skin lightening cosmetics are in hot demand all over the world. Traditionally, skin lighteners contained a chemical called hydroquinone, a synthetic compound which is known to reduce the colour of the skin. However, hydroquinone has now been banned for use in cosmetics in the EU and concerns were raised in the USA over its potential role as a carcinogen and enhancer of skin sensitivity. As people who typically want to lighten their skin use these products over a longer period of time, this raises additional health concerns caused by long-term chronic use.
Luckily, alternative naturally-occurring compounds such as glabridin have been found to be successful at lightening the colour of skin. Studies have shown that glabridin also prevents UV-B induced pigmentation and exerts anti-inflammatory effects on the skin.
Liquorice in Skincare: Liquiritin
By now you’re probably thinking – OMG, what more can this miracle herb do for my skin?! Well, bear with me because I’m not finished.
Liquorice also contains a compound called liquiritin. This chemical is particularly useful for treating melasma. Melasma is a tan or dark skin discolouration and is particularly common in women, especially those who live in areas of intense sunlight exposure, are pregnant or are taking oral contraceptives.
Unlike glabridin, it doesn’t effect tyrosinase but causes depigmentation by other mechanisms. A split-face study of 20 women in Egypt with melasma evaluated the efficacy of liquirtin and reported that 80% of the treated cases had an excellent response, with mild irritation (inflammation and a slight burning sensation) occurring in 20% of those tested, suggesting a possible regimen of 1 gram per day for 4 weeks in order to treat their skin discolouration.
Another study in Pakistan compared the use of liquiritin to hydroquinone for treating melasma and found that liquiritin was more successful than hydroquinone.
So not only is liquorice anti-inflammatory but it also contains compounds that enhance skin penetration, provide skin lightening properties and treat melasma. I’ve covered three of the main constituents of liquorice, but there are many more such as Isoliquiritin, Liquiritigenin, Isoliquiritigenin and Asparagine, to name but a few.
In my opinion, this plant is a perfect example of where its use as a whole plant can provide multiple beneficial skincare functions. The main struggle for any cosmetics formulator will be making sure that it penetrates into your skin far enough to make sure it has the desired anti-ageing, anti-inflammatory or skin lightening effect.
Another point to be aware of is that it is best to be cautious with the amount of liquorice used in cosmetic preparations. Liquorice toxicity in food has been known to occur when some people have gone on a liquorice binge. While any topical use of liquorice will have a different effect to you eating it, it is still best to stick to about 0.5% – 1.0% in your skincare.
Have you ever used skincare that contains liquorice? How did it work for you?