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Licorice Extract (glabridin / liquiritin, topical)
A licorice-root botanical applied to the skin for brightening and soothing — a topical cosmetic, not the ingested licorice supplement. Its actives glabridin (a tyrosinase inhibitor) and liquiritin (which disperses melanin) plus anti-inflammatory compounds give it a coherent rationale for fading hyperpigmentation and calming redness. The honest framing: the human evidence is genuinely thin — one small split-face RCT of liquiritin cream for melasma, one comparative trial of a licorice-containing blend that nearly matched hydroquinone, and otherwise preclinical work. A gentle, plausible brightener whose isolated effect is poorly established and rests on small, dated, mostly combination studies.
Topical cosmetic ingredient — not a dietary supplement
Licorice Extract / Glabridin (topical) is a topical cosmetic ingredient, not a supplement you take internally and not a drug. It is sold legally in skincare products to affect the appearance of skin (such as wrinkles). The evidence below comes mostly from small, often industry-funded studies of topical application, so treat the effect sizes cautiously. This page is for transparency and education, not a recommendation.
What the evidence says
Most Licorice Extract / Glabridin (topical) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality randomised trials published 1998–2021 with a typical study size of 56 participants.
Based on 4 studies · 2 RCTs · 76 total participants
Confidence
Low confidenceBy outcome
A coherent mechanism (glabridin tyrosinase inhibition + anti-inflammatory; liquiritin melanin dispersion) and a small vehicle-controlled human RCT for melasma support a brightening/soothing effect — but the human base is tiny, dated, and largely combination-based, with no large isolated-ingredient trial.
Topical licorice (Glycyrrhiza glabra) extract is used as a gentle skin-brightening and soothing active; its key cosmetic actives are glabridin and liquiritin, plus anti-inflammatory flavonoids. This entry covers TOPICAL cosmetic use (not the oral licorice supplement).
Mechanistically the rationale is sound: glabridin inhibits tyrosinase (the rate-limiting melanin enzyme) and, in animal skin, suppressed UVB-induced pigmentation and erythema, with anti-inflammatory activity; liquiritin acts more by dispersing/redistributing existing melanin.
The human evidence, however, is thin and dated. The foundational trial (Amer & Metwalli, 2000) was a small (n=20) split-face, vehicle-controlled study of liquiritin cream for melasma applied twice daily for four weeks.
A better-powered comparative study (Costa et al., 2010; n=56) tested a multi-ingredient botanical blend (emblica + licorice + belides) against hydroquinone 2% and found no significant difference in depigmentation with fewer adverse events — but licorice was not isolated.
A 2021 systematic review of natural depigmenting agents lists licorice among ingredients with supporting data while explicitly flagging that the trials are few, small, and short.
So the honest summary: topical licorice/glabridin is a gentle, mechanistically plausible brightener and soother, but its isolated efficacy is poorly established — the human data are a single small dedicated RCT plus combination studies. None of this is a health claim.
It is listed under Beauty & Appearance so it is discoverable, but is sandboxed out of ingestible-supplement stacks and the schedule optimizer; it carries a cosmetic badge and a topical-only disclaimer.
Glabridin, a key licorice flavonoid, inhibits tyrosinase at low concentrations without affecting DNA synthesis, and topical glabridin suppressed UVB-induced pigmentation and erythema in animal skin. This is the basis for licorice's brightening and soothing reputation.
Liquiritin acts more by dispersing and redistributing existing melanin than by blocking its synthesis, and licorice flavonoids have anti-inflammatory activity (inhibiting superoxide and cyclooxygenase) — complementing the pigment-evening and calming effects.
Topical licorice is generally considered low-concern and is often suggested as a gentle brightener; discuss your routine with a clinician.
Usually soothing and well tolerated; still patch-test as with any botanical.
Manage expectations — licorice is a gentle, modest brightener; hydroquinone, azelaic acid, or clinician-guided options have stronger evidence, and daily sunscreen is essential.
Licorice is gentle and soothing and layers well with other brighteners; combining many actives can still irritate sensitive skin. Not a systemic interaction — it is not ingested here.
Tip: Uncommon; patch-test and discontinue if a reaction occurs.
Licorice Extract / Glabridin (topical) has an evidence score of 4/10 — emerging evidence based on 4 indexed studies. A licorice-root botanical applied to the skin for brightening and soothing — a topical cosmetic, not the ingested licorice supplement. Its actives glabridin (a tyrosinase inhibitor) and liquiritin (which disperses melanin) plus anti-inflammatory compounds give it a coherent rationale for fading hyperpigmentation and calming redness. The honest framing: the human evidence is genuinely thin — one small split-face RCT of liquiritin cream for melasma, one comparative trial of a licorice-containing blend that nearly matched hydroquinone, and otherwise preclinical work. A gentle, plausible brightener whose isolated effect is poorly established and rests on small, dated, mostly combination studies. Representative study: PMID 34840659.
The commonly studied dose of Licorice Extract / Glabridin (topical) is Topical cosmetic only. Licorice extracts (standardized to glabridin or as liquiritin) are used in brightening serums and creams applied to clean skin once or twice daily, often with other brighteners and daily sunscreen. There is no oral or systemic dose in this cosmetic context. This library does not provide an ingestion protocol.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Licorice Extract / Glabridin (topical) — consistent daily use matters more than the time of day. Topical licorice is a leave-on brightening/soothing botanical with no meal-timing relationship; pairing with daily sunscreen matters more for pigment goals.
Licorice Extract / Glabridin (topical) is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects are uncommon and include mild local irritation or allergy. Use caution if any of these apply to you: For topical (skin) use only — not for ingestion in this context; Known allergy or sensitivity to licorice or the formulation; Application to broken or irritated skin until healed.
Centella Asiatica (Cica)
Mostly mechanism / observationalA viral 'cica' botanical applied to the skin for soothing, barrier repair, wound healing, and anti-aging — a topical cosmetic, not (in this context) the oral gotu kola supplement. Centella asiatica's active triterpenes (madecassoside, asiaticoside, asiatic/madecassic acid) stimulate collagen and calm inflammation. The honest framing: the best human evidence is for wound healing and post-procedure soothing; the anti-aging signal rests on a single small (n=20) trial that combined madecassoside with vitamin C, scar/stretch-mark evidence is weak, and much of the mechanism is in-vitro/animal. Contact allergy is uncommon but documented. A genuinely promising, well-tolerated soothing botanical with moderate, still-maturing evidence.
Tea Tree Oil (topical)
Mostly mechanism / observationalA plant essential oil applied to the skin for acne — the best-evidenced 'natural' acne topical, though that's a low bar. The honest framing: two small randomized trials back it. A classic 1990 RCT found 5% tea tree oil reduced acne lesions about as much as 5% benzoyl peroxide with fewer side effects (but slower to work), and a 2007 placebo-controlled RCT found 5% tea tree oil gel several times more effective than placebo. Its active terpinen-4-ol is genuinely antibacterial against the acne bacterium. But the evidence is small, dated, and rated low-quality by Cochrane; there's no large modern standardized trial, products vary widely in composition, and tea tree oil is a well-recognized cause of allergic contact dermatitis — especially as it oxidizes with age. A reasonable gentle option for mild acne, not a first-line treatment.
Bakuchiol
Mostly mechanism / observationalA plant-derived topical skincare active marketed as a gentler 'retinol alternative' — a leave-on cosmetic applied to the skin, NOT ingested. Bakuchiol is a meroterpene purified from the seeds of Psoralea corylifolia (babchi). Despite no structural resemblance to retinoids, gene-expression studies show it behaves like a functional retinol analogue, switching on collagen genes. The headline evidence is one good 12-week randomized, double-blind trial (44 people) in which bakuchiol matched retinol for reducing wrinkles and pigmentation while causing less stinging and scaling. The honest framing: that single 44-person study carries most of the weight. The rest of the human evidence is thin — small, often unblinded or uncontrolled trials, several testing bakuchiol only inside multi-ingredient products, and many industry-linked; a 2024 systematic review judged the body of evidence high-risk-of-bias and not poolable. These are cosmetic appearance outcomes, not health outcomes. (Note: purified topical bakuchiol is distinct from oral Psoralea corylifolia, which carries hepatotoxicity and phototoxic-furocoumarin concerns.)
Green Tea / EGCG (topical)
Mostly mechanism / observationalGreen tea polyphenols (chiefly EGCG) applied to the skin as an antioxidant for photoprotection, acne, and anti-aging — distinct from the oral green tea extract. The honest framing: there's a real but modest, mostly small-trial signal. Controlled human studies show topical green tea reduces UV-induced redness, sunburn cells, and oxidative/DNA damage; the best acne work pairs solid mechanism data with a positive split-face RCT; and the antioxidant/anti-inflammatory mechanism (plus MMP suppression relevant to wrinkles) is coherent. But the clinical trials are small, often uncontrolled or pilot/split-face, much of the anti-aging evidence is in-vitro, and EGCG is chemically unstable and penetrates skin poorly — so real-world potency depends heavily on a stabilized formula. Best used as an antioxidant adjunct (alongside sunscreen), not a standalone treatment.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 4 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.