Comparison

Glycolic Acid vs Kojic Acid

Glycolic acid exfoliates pigmented cells off the surface. Kojic acid blocks new pigment being made. Which suits your marks, and how to use both.
Written & medically reviewed by the Dermapedia team
At a Glance

Glycolic acid lifts dead, pigmented cells off the surface of the skin. It fades marks and smooths rough texture at the same time, so it does more than one job. Kojic acid blocks your skin from making new pigment. It is a spot-fader and very little else, which makes it the more direct tool when dark marks are your only complaint.

Glycolic acid
Also called AHA, alpha hydroxy acid, glycolic peel
Kojic acid
Also called kojic dipalmitate, kojic acid soap

What you do

A few nights a week

A toner, serum or pad left on at night. Some people have a stronger peel in a clinic every few weeks instead.

Once or twice a day, on the marks

A serum, cream or cleansing bar. Serums are left on; bars get rinsed away, so they do less.

What you will see

Smoother, brighter skin

Softer texture, less dullness, smaller-looking pores, and a slow fade of surface discolouration.

Dark spots losing contrast

Sun spots, melasma patches and marks left by old acne gradually stop standing out from the skin around them.

What it will not do

It will not stop new pigment

Glycolic acid removes what is already on the surface. It does nothing to slow the cells that are making more.

It will not smooth texture

Kojic acid does not exfoliate, so rough, bumpy or dull skin needs something else alongside it.

How long until it works

Two to four weeks for texture

Brightness comes early. Discolouration takes a few months of steady use.

Around 6 to 10 weeks

Fading is gradual throughout. Anything faster usually means the mark was very superficial.

Both
Neither will beat new sun exposure. Without daily sunscreen, both are working against a tap you have left running.

How long it lasts

As long as you keep using it

Turnover returns to its usual pace within a few weeks of stopping.

As long as you use it and stay sun-safe

Spots return if the trigger — sun, inflammation or hormonal change — is still there.

The downside

Stinging and sun sensitivity

It can sting on application and it makes skin more sensitive to sun. Daily sunscreen is not optional with an AHA.

Irritation, and it goes brown

It can sting and cause a rash in some people, more so with long use. It also oxidises easily, so the product itself darkens and loses strength.

Cost

Inexpensive at home, more in clinic

Drugstore serums, toners and pads are cheap. A course of in-clinic peels costs considerably more.

Inexpensive

Sold in drugstore serums, creams and soaps. There is no premium version that works differently.

The at-home or drugstore version

The same acid, turned down

Drugstore glycolic acid works at the surface and works slowly. A clinic peel is the same molecule, stronger and buffered differently, so it reaches deeper and works faster — with a few days of flaking as the trade.

Drugstore is the only version

Kojic acid is an over-the-counter ingredient with no prescription form. A clinician treating stubborn pigment reaches for hydroquinone or tranexamic acid instead.

They work at opposite ends of the same problem

Glycolic acid removes pigment that has already been made: It loosens the bonds holding dead surface cells together, and those cells take their pigment with them when they go.

Kojic acid stops pigment being made in the first place: Tyrosinase, the enzyme that builds melanin, needs copper to work. Kojic acid grabs that copper and the production line slows down.

So one clears the backlog and the other closes the tap: That is why they are often used together rather than chosen between.

Which one for which complaint

Choose glycolic acid if your skin is dull, rough or uneven overall: Bumpy texture, blackheads, a general lack of glow and mild surface discolouration are its territory.

Choose kojic acid if defined dark spots are the whole problem: Sun spots, melasma and old acne marks on skin that is not especially reactive respond to it, and it does not thin the surface.

Choose glycolic acid if you also want the anti-ageing effect: Regular AHA use softens fine lines a little. Kojic acid does nothing for lines at all.

Using them together

Layering both at once is the usual mistake: An exfoliating acid opens the door for the brightener, which sounds efficient and mostly produces a stinging, red face.

Alternating nights is the workable version: Glycolic acid two or three nights a week, kojic acid on the nights in between, is a routine most skin tolerates.

Deeper skin tones need more care with the acid than the brightener: Irritation itself can trigger extra pigment, so a strong glycolic peel on deeper skin is a decision for a clinician rather than a shopping cart.

Before you start either one

Introduce one new ingredient at a time and give it eight weeks

Start two or three nights a week rather than daily

Wear sunscreen every morning — mandatory with glycolic acid, sensible with both

Keep kojic acid products sealed and out of the light, and replace them once they darken

Take a photo on day one in the same light, because slow fading is hard to judge from memory

Stop and reassess if the skin around a treated spot starts looking paler than the rest

Related

Questions people ask

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Which is better for dark spots, glycolic acid or kojic acid?
Kojic acid is the more direct choice, because it stops new pigment being made. Glycolic acid fades marks more slowly but also smooths texture, so it does more overall.
Can I use glycolic acid and kojic acid together?
Yes, but usually on alternate nights rather than layered. Using both at once is the most common cause of stinging and redness.
Which one is gentler?
Kojic acid is gentler on the skin barrier, since it does not exfoliate or increase sun sensitivity. It can still cause a rash in some people with long use.
Why has my kojic acid serum turned brown?
Kojic acid oxidises when exposed to air and light. A serum that has darkened has lost strength and is worth replacing. Keeping it sealed and out of sunlight slows this down.
Do I need sunscreen with these?
With glycolic acid, yes — it makes skin more sensitive to sun. With kojic acid, sunscreen is what makes the fading hold, since new sun exposure rebuilds the spots you are treating.
How long before I see a difference?
Glycolic acid improves texture in two to four weeks. Both take six to twelve weeks to shift pigment, so photograph the area on day one to judge it fairly.