Licorice Root Extract

Licorice root is one of the better-evidenced botanicals in skincare, with activity through several distinct routes rather than a single vague antioxidant claim.

The active constituents

Licorice contains several groups of compounds, and they do different things.

Glabridin is the most studied for skin tone. It inhibits tyrosinase, the enzyme that initiates melanin synthesis, and has anti-inflammatory activity. Most research on licorice and pigmentation concerns glabridin specifically.

Liquiritin works differently, appearing to disperse existing melanin rather than prevent its formation.

Glycyrrhizin and its derivative glycyrrhetinic acid are the compounds behind licorice's anti-inflammatory reputation. Glycyrrhetinic acid is used in dermatological preparations for irritated skin.

Licochalcone A has antioxidant and anti-inflammatory activity and appears in formulations aimed at redness.

Species matters

This is where labels become unhelpful. Glycyrrhiza glabra, European licorice, is the richest source of glabridin. Glycyrrhiza uralensis, Chinese licorice, has a different constituent profile with more licochalcone A and considerably less glabridin.

Both appear on ingredient lists as licorice root extract with only the species name distinguishing them. A product using uralensis is drawing more on the anti-inflammatory and antioxidant side than on the glabridin pigmentation route.

Extraction and standardisation

As with all botanicals, the INCI name tells you the plant and the part used. It does not tell you the extraction method, the solvent, or the concentration of any active constituent. Glabridin content in commercial extracts varies by more than an order of magnitude between suppliers.

This is a general limitation of botanical ingredients rather than a criticism of any particular product, but it is the reason percentage comparisons between botanical extracts are close to meaningless.

Topical versus oral

Worth distinguishing. Oral licorice consumed in quantity can raise blood pressure and lower potassium through glycyrrhizin's effect on mineralocorticoid metabolism. That is a well-documented pharmacological effect of ingestion. It does not apply to cosmetic topical use at cosmetic concentrations.