Kojic acid is on the label of a great many Indian creams, serums and soaps sold for dark spots and tan. It is a real ingredient with a real mechanism, and also one that irritates more people than most of its alternatives. Both halves are worth knowing before buying anything with it.
What kojic acid is
Kojic acid is made by certain fungi as they ferment. The name comes from koji, the mould used in Japan to ferment rice for sake and soy sauce, where it was first identified. For cosmetics it is produced by fermentation and then purified.
It is a small, water-soluble molecule. It is also unstable: exposed to air and light, it turns yellow and then brown, and a product that has darkened in the jar has lost much of what it was bought for.
How it works
Skin makes pigment with the help of an enzyme called tyrosinase. Tyrosinase needs copper to work, and kojic acid binds that copper. With the enzyme slowed, less new pigment is made.
That is the whole mechanism, and it sets the limits. Kojic acid does nothing to pigment already sitting in the skin. It reduces how much new pigment is added, and existing marks fade as skin renews itself, slowly. How melanin production works explains the process it interrupts.
What it is used for
- Dark spots left by sun or by old pimples. How to fade dark spots covers which kind of mark responds to what
- Uneven tone more generally, usually in combination with other ingredients
- Melasma, as one part of a plan a doctor oversees. Melasma: where cosmetics stop explains why a cream alone rarely holds it
- Tan, though a tan fades by itself with sun protection, and kojic acid only stops more pigment being added. Ingredients that fade a tan puts it alongside the others
None of these work without sunscreen. Sun exposure keeps telling the skin to make pigment, faster than any cream can slow it down.
What it cannot do
It does not change your natural skin tone. Products that use it to promise "fairness" are selling something the chemistry does not deliver, and what skin brightening means covers the difference.
It does not remove scars, open pores or dullness from dryness. And in a soap it barely gets a chance, because it is rinsed away within a minute. Do tan removal soaps work goes into that.
Side effects
The common one is irritation: redness, stinging, itching or dryness where it is applied. Kojic acid is also a known cause of contact allergy, which is different from irritation. An allergy can appear after weeks of uneventful use, and once it has started it tends to return every time the skin meets the ingredient.
Irritated skin can darken, which is the opposite of what the product was bought for. On Indian skin this is the most common way a pigment product backfires.
So:
- Patch test a new product on the inner arm for a few days first
- Start every other night, and build up only if the skin stays calm
- Keep it away from broken or freshly waxed skin
- Stop at the first sign of a rash, and see a doctor if it spreads
Pregnancy is a common question. There is little research either way, so ask your doctor before starting it. Pigmentation in pregnancy covers the wider picture.
How it compares
Alpha arbutin slows the same enzyme by a different route, and tends to irritate less. Kojic acid vs alpha arbutin compares the two directly.
Vitamin C works on pigment and also acts as an antioxidant, with its own stability problems. Kojic acid vs vitamin C sets them side by side.
Niacinamide works further along, by reducing how much pigment moves from the cells that make it to the surface cells. Because it acts at a different step, it pairs well with kojic acid. Does niacinamide lighten skin explains what it does and does not do.
Who should skip it
- Anyone who has reacted to it before
- Sensitive or eczema-prone skin, where the alternatives above are gentler starting points
- Skin that is already irritated from another active. Let it settle first. Over-exfoliated skin describes the signs
Where the Cham range fits
No Cham product contains kojic acid.
The Brightening Face Mask contains alpha arbutin alongside two forms of vitamin C, and all five products contain niacinamide. Those are the routes the range takes instead.
