Quick Comparison
| Lactic Acid | Tranexamic Acid | |
|---|---|---|
| Typical Concentration | Concentrations: 5-12% for daily use. 30-50% for professional peels. Start with 5% every other night. The Ordinary offers 5% (gentle) and 10% (moderate) options. Always use SPF during the day. | Topical: 2-5% in serum or cream, applied twice daily. Oral (off-label for melasma): 250 mg twice daily — requires medical supervision. Can be combined with other brightening agents. Results visible at 8-12 weeks. Especially effective for melasma. |
| Application | Topical (serum, peel, toner). Apply to dry skin at night. Follow with moisturizer. | Topical (serum, cream) or oral (tablets, off-label). Topical preferred for safety. Oral is more effective but carries systemic risks. |
| Research Papers | 10 papers | 10 papers |
| Categories |
Mechanism of Action
Lactic Acid
Lactic acid (90 Da, larger than glycolic acid) exfoliates via the standard AHA mechanism: chelating calcium at corneodesmosomes and promoting desquamation through protease activation. Unlike glycolic acid, lactic acid is a natural component of the skin's natural moisturizing factor (NMF) and functions as a humectant, drawing water into the stratum corneum through hygroscopic binding. It inhibits tyrosinase enzyme activity in melanocytes, providing mild brightening. At higher concentrations (10%+), lactic acid upregulates serine palmitoyltransferase and glucosylceramide synthase in keratinocytes, stimulating ceramide synthesis and improving barrier lipid composition. It also enhances filaggrin proteolysis to NMF components. This dual action—exfoliation plus barrier support—makes it the most moisturizing AHA and clinically useful for dry, sensitive, or barrier-compromised skin.
Tranexamic Acid
Tranexamic acid (TXA) is a lysine analogue that competitively inhibits plasminogen activation—binding lysine-binding sites and preventing conversion to plasmin by tPA and uPA. Plasmin normally activates multiple pathways: converts latent TGF-beta to active form, stimulates keratinocyte release of arachidonic acid and prostaglandins (PGE2, PGF2-alpha), and increases SCF and bFGF—all stimulating melanocyte proliferation and melanogenesis. By blocking plasmin, TXA interrupts this paracrine cascade, reducing melanin through a mechanism independent of tyrosinase. TXA also inhibits VEGF and reduces angiogenesis—addressing melasma's vascular component. May reduce UV-induced plasmin in keratinocytes. This unique mechanism makes TXA synergistic with tyrosinase inhibitors for stubborn melasma.
Risks & Safety
Lactic Acid
Common
Mild stinging, redness — less than glycolic acid at equivalent concentrations. Sun sensitivity.
Serious
None at cosmetic concentrations.
Rare
Over-exfoliation with daily high-concentration use.
Tranexamic Acid
Rare
Topical form has minimal systemic absorption and low risk.
Full Profiles
Lactic Acid →
A gentle AHA derived from milk that provides chemical exfoliation plus hydration — a unique dual benefit. Lactic acid has a larger molecular size than glycolic acid, so it penetrates more slowly and causes less irritation, making it ideal for sensitive skin and AHA beginners. It also has humectant properties, drawing moisture into the skin as it exfoliates.
Tranexamic Acid →
Originally an oral medication for heavy menstrual bleeding, tranexamic acid (TXA) has emerged as one of the most effective treatments for melasma and stubborn hyperpigmentation that does not respond to conventional treatments. It works through a unique mechanism — blocking plasmin-mediated stimulation of melanocytes — that is different from tyrosinase inhibitors, making it an excellent combination partner.