The percentage of niacinamide that has been studied for uneven tone is 2 to 5 percent, and 10 percent is the well-tolerated upper end; for vitamin C, 5 percent ascorbic acid has been compared head to head with prescription strengths and holds up, while 15 to 20 percent mostly adds sting. The number that matters is not the biggest one on the shelf. It is the highest one you can use every day on your skin without irritation, because on melanin-rich skin irritation is itself a cause of dark marks.
What "percentage" means on a skincare label
A printed percentage is the share of the formula, by weight, that is that ingredient. A "10% niacinamide" cream is one-tenth niacinamide and nine-tenths everything else: water, emollients, thickeners, preservatives. That is the only claim on the front of a product that you can pin down; "with vitamin C," "infused with," "powered by" and "vitamin C complex" tell you the ingredient is present and nothing about how much.
Two things to check before the number impresses you. First, the form: "vitamin C" covers L-ascorbic acid and half a dozen derivatives that behave differently. Second, whether anyone outside the company has confirmed the number. Ask the brand for the lab report and look for an assay of the active. Our guide to what independent lab testing means explains that part.
The jar in the picture is our Brightening Cream; the two numbers on the front are the ones this article is about.
How to read the ingredient list
Ingredients are listed in descending order of weight down to 1 percent. Below 1 percent, they can appear in any order. That rule tells you more than most marketing does.
- If an active sits in the first five or six names, it is present at a meaningful amount.
- If it sits after the preservative (phenoxyethanol, sodium benzoate, potassium sorbate) or after the fragrance, it is almost certainly under 1 percent.
- Water is usually first. In a 10 percent niacinamide serum, niacinamide is usually second or third.
- A long list of botanical extracts at the end is decoration. Nice, sometimes calming, rarely at a dose that matters.
The longer version, including what the names of preservatives and emulsifiers mean, is in how to read a skincare label.
What percentage of niacinamide is effective?
Niacinamide (vitamin B3) has been studied for uneven tone at 2, 4 and 5 percent, and those strengths did the job in the research: supporting the barrier, helping to keep pigment from transferring into the surface cells, and easing the look of dark patches with regular use. Ten percent is the common upper end in products and is well tolerated by most people; it is where we sit because it gives room for the ingredient to do its work in a cream you apply once a day. Above 10 percent, flushing, stinging and small bumps become more common, and there is no good evidence that 15 or 20 percent does more for tone. On skin that reacts easily, 4 or 5 percent is a fine place to start and 10 is a fine place to end up.
What percentage of vitamin C is effective?
This is where the marketing and the research disagree most. Pure L-ascorbic acid absorbs best at low pH and the absorption levels off around 20 percent, which is where the "20% vitamin C" serums come from. But absorption is not the same as tolerance, and on melanin-rich skin a serum that stings every morning is a serum that causes marks. A randomized study compared a 5 percent ascorbic acid cream with 4 percent hydroquinone for melasma: hydroquinone did more on the pigment score, but roughly two-thirds of the hydroquinone group reported irritation against a small fraction of the vitamin C group. That is the trade we care about. A 5 percent vitamin C you can wear every day under sunscreen, for months, does more over time than a 20 percent one you abandon in a week. Derivatives (sodium ascorbyl phosphate, ascorbyl glucoside, ethyl ascorbic acid) are gentler still at similar percentages and more stable in a cream. Our guide to vitamin C for dark skin covers the forms.
Why "more" backfires on melanin-rich skin
Deeper skin tones make pigment in response to injury, and stinging is injury. A product that is strong enough to cause daily redness is producing exactly the signal that creates new dark marks, while it works on the old ones. That is why high-percentage actives so often disappoint on Black and brown skin: the irritation cancels the benefit. The effective percentage is the highest one that causes no reaction with daily use, and it is lower than the highest one available.
Quick reference: typical product ranges, not trial strengths
The ranges below are what products on the shelf commonly use. They are not the strengths the trials above tested, which were 2, 4 and 5 percent niacinamide and 5 percent ascorbic acid.
- Niacinamide: 2 to 10 percent. Ten is the sensible ceiling.
- Vitamin C (L-ascorbic acid): 5 to 10 percent for daily use on reactive skin; 15 to 20 only if you tolerate it without any sting.
- Vitamin C derivatives: 2 to 10 percent, gentler at the same number.
- Kojic acid: 1 to 4 percent, usually in a wash-off soap.
- Azelaic acid: 10 percent over the counter; higher strengths are prescription.
- Alpha arbutin: 1 to 2 percent.
- Tranexamic acid: 2 to 5 percent.
- Glycolic acid (leave-on): 5 to 10 percent at home, once or twice a week on melanin-rich skin, not daily.
- Salicylic acid: 0.5 to 2 percent.
Ranges are for adults with healthy skin. Start at the bottom of a range, patch test, and only move up if there is no reaction after a couple of weeks of daily use.
How IYASA does it
We print 5% vitamin C and 10% niacinamide on the front of the Brightening Cream because those are the strengths melanin-rich skin can use every single day without the sting that creates new marks, and because a printed number is a number you can hold us to. Every IYASA formula is independently lab-tested (safety screens; the report does not measure the percentages). It sits in a shea butter base so the barrier stays calm while the actives work. For how the two ingredients fit together in one routine, read vitamin C and niacinamide together.
Orders of $39.99 or more come with a free gift: a Kojic soap or a Vitamin C sugar scrub. You can see the cream here.
Frequently asked questions
Is 10% niacinamide too much?
No, for most skin. Ten percent is the upper end of the range that has been studied for tone and it is well tolerated by most people. Above that, flushing and stinging become more common with no clear gain, so there is no reason to chase 15 or 20.
Is 5% vitamin C strong enough?
Yes. A 5 percent ascorbic acid cream has been compared head to head with 4 percent hydroquinone for melasma in a randomized study; it did less on the pigment score but caused far fewer irritation complaints, and irritation on melanin-rich skin is itself a source of marks. For daily use on deeper skin tones, 5 percent is a sensible strength.
Does a higher percentage work faster?
Only up to a point, and past that point it works worse, because the irritation it causes creates new pigment. The most effective percentage is the highest one you can use every single day without stinging, which on melanin-rich skin is usually lower than the marketing suggests.
What does it mean if niacinamide is near the end of the ingredient list?
That it is present at 1 percent or less, since everything under 1 percent can be listed in any order at the end. It is not useless, but it is not the 4 to 10 percent that the studies used, and the brand chose not to print a number for a reason.
Sources
- Hakozaki T and others. The effect of niacinamide on reducing cutaneous pigmentation and suppression of melanosome transfer. 2002: the trials used 2 percent and 5 percent niacinamide; the 5 percent moisturizer reduced the look of dark patches against the same moisturizer without it.
- Navarrete-Solis J and others. Randomized split-face trial of 4% niacinamide against 4% hydroquinone in melasma, 2011: 4 percent niacinamide improved pigment on every patient, with side effects in 18 percent against 29 percent for hydroquinone.
- Espinal-Perez LE, Moncada B, Castanedo-Cazares JP. Randomized split-face trial of 5% ascorbic acid against 4% hydroquinone in melasma, 2004: hydroquinone scored better on patient ratings, color measurements showed no statistical difference, and side effects were reported in 68.7 percent with hydroquinone against 6.2 percent with ascorbic acid.
- Pinnell SR and others. Topical L-ascorbic acid: percutaneous absorption studies. 2001: L-ascorbic acid must be formulated below pH 3.5 to enter the skin, and absorption was maximal at 20 percent.
- DermNet, page on pigment-fading agents: lists kojic acid at 1 to 4 percent.