Tranexamic acid

Tranexamic acid began life as a drug to reduce bleeding. Its route into skincare runs through plasmin: UV exposure raises plasmin activity in keratinocytes, which in turn increases melanocyte-stimulating signals. TXA blocks that pathway[1].

The evidence

A 12-week study of 2 % topical TXA reduced MASI scores and, on histology, decreased epidermal pigmentation and vascularity[1]. A split-face trial of 3 % TXA versus a hydroquinone–dexamethasone combination found similar improvement[2], and liposomal 5 % TXA matched 4 % hydroquinone in another comparison[3].

Trials are small and mostly from a handful of groups, which is why the grade is Moderate rather than Strong. Pairs with niacinamideNiacinamideStrongNiacinamide · Vitamin B3 amideWater-soluble B3 with strong evidence for barrier, tone and sebum; among the most studied topical actives.Open in the Index → and azelaic acidAzelaic acidStrongAzelaic Acid · Dicarboxylic acidPrescription-grade evidence for rosacea and acne at 15–20 %; cosmetic versions run lower.Open in the Index →; pointless without sunscreen.