“Licorice root” can refer to different species, extraction methods, and compounds. Glabridin is a flavonoid-rich component associated with some melanogenesis research. Licochalcone A is a different compound, associated with the licorice species Glycyrrhiza inflata. Liquiritin is another compound with different evidence. A product that says “licorice extract” does not disclose which one was tested (Yokota et al.; Weber et al.).

The useful cosmetic verdict is narrow: some named preparations have early signals for visible tone, redness, or comfort. There is no universal “licorice brightening” result (Yokota et al.; Weber et al.; systematic review).

Glabridin: interesting mechanism, not a human product trial

Yokota and colleagues studied glabridin in cultured murine melanoma cells and guinea-pig skin. Glabridin inhibited tyrosinase activity in the cell model, and topical 0.5% glabridin reduced UVB-induced pigmentation and erythema in guinea pigs (PubMed).

That is mechanistic and animal evidence, not proof that a retail serum with unspecified licorice extract will change human skin tone. The authors were all affiliated with Kanebo’s Basic Research Laboratory, a commercial employer context worth seeing when reading the result. The study also tested purified glabridin, not a generic root extract.

Licochalcone A: a different cosmetic question

A prospective randomized vehicle-controlled study tested cosmetic formulations containing licochalcone A in post-shaving irritation and UV-induced erythema models. The abstract reports a significant reduction in erythema versus vehicle (Weber et al.).

The paper reports separate volunteer cohorts. A controlled, single-blind, randomized split-face stinging test enrolled 24 volunteers (21 women and 3 men, ages 19–59). A separate 38-person study tested a combination containing licochalcone-A-rich licorice extract plus 4-t-butylcyclohexanol against vehicle in induced-irritation models (Sulzberger et al.).

These are useful cosmetic signals for a named formula and a narrow induced- irritation endpoint. They do not show that licochalcone A alone caused the change, that every licorice extract contains enough of it, or that it treats rosacea, acne, eczema, or any other disease. (Weber et al.; Sulzberger et al.)

What the human tone literature can and cannot say

A systematic review of natural ingredients for hyperpigmentation summarizes small controlled studies involving licorice-derived preparations such as liquiritin and glabridin. It reports human signals, but the studies are heterogeneous in material, formula, population, and outcome (systematic review).

The material-specific evidence matters: an ingredient can have a reasonable mechanism and some human signals while still failing the label-transfer test. A study of a standardized glabridin preparation is not a study of every product with Glycyrrhiza root extract. A licochalcone-A-rich calming formula is not a glabridin brightening serum (Yokota et al.; systematic review).

How to read the product label

Look for the exact INCI name, species if given, standardized marker compound, and whether the brand names a human study of the finished formula. Do not infer the glabridin or licochalcone content from “licorice root” alone. The label also cannot reveal the extraction solvent, stability, dose, vehicle, or whether a study formula matches the bottle (Yokota et al.; Weber et al.).

Keep the cosmetic endpoint honest: a product may support the appearance of more even tone or temporarily calmer-looking redness. It does not bleach skin, erase all pigmentation, replace sunscreen, or treat an inflammatory diagnosis. Stop a product that stings, burns, or causes a rash and seek professional care for a persistent reaction.

Evidence is mixed: the compounds have plausible and some controlled human cosmetic signals, but whole-root labels remain too vague to inherit those results. Unknowns include species, extraction, standardization, concentration, vehicle, stability, skin-tone representation, and the identity of the compound actually present.

Sources

This answer summarizes cosmetic ingredient evidence. It is not medical advice.