Kojic Acid

Kojic acid is produced by fungi during fermentation, notably koji, the mould used to make sake and soy sauce, and is usually found in brightening products to improve the look of discolouration and pigmentation. It helps even the look of skin tone and fade the appearance of dark spots. It works gradually, and is often paired with other brighteners such as vitamin C, niacinamide and liquorice root.

Kojic acid is not an exfoliant. In laboratory studies it binds copper, which tyrosinase, the enzyme involved in making pigment, needs in order to work; it doesn't reduce the number of pigment cells (melanocytes) themselves. Used consistently, it helps fade the look of dark spots, post-blemish marks and uneven tone, especially with daily SPF to stop new pigment forming. Pure kojic acid can discolour and lose strength in the jar, so some formulas use a more stable form, kojic dipalmitate.