Quick Comparison
| Kojic Acid | Licorice Root Extract | |
|---|---|---|
| Typical Concentration | Concentrations: 1-4%. Kojic dipalmitate is a more stable ester form but less potent. Apply once or twice daily. Often combined with other brightening agents (arbutin, vitamin C, niacinamide). Results visible at 4-8 weeks. | Concentrations vary; glabridin at 0.1-0.4% is the most active brightening component. Full extract at 1-4%. Apply morning and/or night. Safe for all skin types. Often combined with niacinamide and arbutin for enhanced brightening. |
| Application | Topical (serum, cream). Store in airtight, opaque packaging. Discard if the product turns brown. | Topical (serum, cream, toner). Very stable in formulation. Compatible with most active ingredients. |
| Research Papers | 10 papers | 10 papers |
| Categories |
Mechanism of Action
Kojic Acid
Kojic acid (5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) inhibits tyrosinase through copper chelation—tyrosinase is a type-3 copper enzyme requiring two copper ions to catalyze tyrosine to L-DOPA and L-DOPA to dopaquinone. By sequestering copper, kojic acid renders tyrosinase inactive. May also inhibit tyrosinase-related protein-1 (TRP-1). Exhibits direct antioxidant activity, scavenging superoxide and hydroxyl radicals. Relatively unstable—oxidizes with air and light, forming brown degradation products that lose activity; opaque, airtight packaging and low pH improve stability. Kojic dipalmitate is a more stable ester but requires enzymatic cleavage, reducing potency. Contact sensitization can develop with prolonged use.
Licorice Root Extract
Glabridin competitively inhibits tyrosinase by binding copper active site (CuA, CuB), blocking tyrosine to L-DOPA hydroxylation and DOPA to dopaquinone oxidation. Also inhibits tyrosinase-related protein 1 (TRP-1). Liquiritin disperses existing melanin via melanosome transfer inhibition and autophagy pathway upregulation in keratinocytes. Glycyrrhizin inhibits COX-2 and 5-lipoxygenase, reducing prostaglandin and leukotriene production. Multi-mechanism brightening: tyrosinase inhibition, melanin dispersal, anti-inflammation. Unlike hydroquinone, no melanocyte cytotoxicity — suitable for long-term use and all skin tones. Glabridin has free radical scavenging antioxidant activity. Glycyrrhizin's 11-beta-HSD inhibition has minimal systemic effect with topical use.
Risks & Safety
Kojic Acid
Common
Contact sensitization (developing an allergy over time with repeated use), redness, irritation.
Serious
Contact dermatitis in sensitized individuals.
Rare
Paradoxical darkening in very sensitive skin types.
Licorice Root Extract
Common
Very well-tolerated.
Serious
None documented topically. Oral licorice (glycyrrhizin) can elevate blood pressure, but topical use does not have this effect.
Rare
Allergic contact dermatitis.
Full Profiles
Kojic Acid →
A natural brightening agent produced as a byproduct of sake and soy sauce fermentation. Kojic acid inhibits tyrosinase by chelating copper, which is required for the enzyme's active site. It is one of the most effective OTC alternatives to hydroquinone for treating hyperpigmentation, melasma, and age spots, though it is less stable in formulation and can cause contact sensitization over time.
Licorice Root Extract →
A natural brightening and anti-inflammatory ingredient derived from Glycyrrhiza glabra root. The key actives — glabridin, liquiritin, and glycyrrhizin — inhibit melanin production, reduce inflammation, and soothe irritation. Licorice root is one of the most effective and gentle brightening ingredients available, with lower irritation risk than vitamin C or hydroquinone.