Tranexamic acid vs kojic acid

Both ingredients are used for a more even-looking tone, but they act at different points in the pigment pathway and behave very differently in a formula.

Tranexamic acid is a synthetic derivative of the amino acid lysine. In skin it reduces plasmin activity in surface cells after UV exposure or irritation. Plasmin is one of the signals that tells pigment cells to increase output, so damping it lowers the trigger rather than blocking the enzyme. It is water-soluble, stable across normal formulation pH, colourless, and has a good tolerability record in the topical studies published so far, which typically use 2–5% over 8–12 weeks. Occasional dryness or mild irritation is the most common complaint. In Japan it is an approved quasi-drug active for tone concerns.

Kojic acid is produced by fermentation, historically by the moulds used to make sake and soy sauce. It inhibits tyrosinase, the copper-dependent enzyme that produces pigment, by binding the copper at its active site. That direct action is why it has a long history in tone products. Its weaknesses are practical: it oxidises readily and browns in the bottle, it is light-sensitive, and it is a recognised contact sensitiser, with irritation and allergic reactions reported more often as concentration and duration increase. Kojic dipalmitate, a more stable ester, is often used instead, though whether it converts back to kojic acid in skin is not well established.

Regulation reflects that record. The EU’s Scientific Committee on Consumer Safety concluded that 1% kojic acid in face and hand creams is safe, and, to our understanding, a 2024 amendment to the Cosmetics Regulation added a 1% limit to Annex III. We are not aware of a specific concentration limit for either ingredient in India, where both are used in cosmetics, and tranexamic acid is not restricted in the EU annexes as far as we know. Rules change; check the current text before relying on this.