Can you use Niacinamide and Vitamin C (Ascorbic Acid) together?

Yes! (For most people.)

Niacinamide and ascorbic acid on their own are great skin care ingredients. Ascorbic acid is not only a good water-soluble antioxidant, but may also increase production of collagen in the skin which can help mitigate some of the damaging effects caused by UV exposure.

Niacinamide is a good anti-inflammatory which makes it useful for treating inflammatory conditions like acne and has been shown to increase naturally occurring moisturizers in the skin.

They’re both very effective at reducing hyperpigmentation of the skin – it’s easy to see why people would want to use the two of them together.

If you Google Niacinamide and Vitamin C, you’ll get some posts about not combining them. The worry is that they form a 1:1 complex and cancel out each other’s skin benefits.

There are two main chemical reactions that occur when you mix niacinamide and ascorbic acid. The first occurs when you mix niacinamide with any acid (or base), and that’s the conversion of niacinamide to niacin. This takes a long time and is more of a concern for manufacturers that are using niacinamide in acidic products.

It’s possible that niacin is just as effective as niacinamide, but it has the side effect of activating Langerhan cells in the skin. This leads to the release of prostaglandins and dilation of the blood vessels, which causes the skin to flush with redness and tingle. This flushing and tingling is temporary, but can be uncomfortable and potentially problematic for someone with inflammatory acne or erythema.

The second concern is the formation of a complex between niacinamide and ascorbic acid. I think the worry is that this complex is no longer effective in benefiting the skin, and I’ve also seen concerns that it may produce hydrogen peroxide which can lead to skin cell death.

I took a look at the research to get a better understanding of these two chemical reactions. It is important to note that a few of these papers are old, so they don’t use newer visualization techniques that can help us quantify chemical changes and structures more accurately.

Hydrolysis of Niacinamide to Niacin

Amides, like niacinamide, are very stable compounds. This stability means it takes a lot of heat and concentrated acids or bases to get niacinamide to turn into niacin (also known as nicotinic acid).

I’m going to do a separate post that will explain this more, but the important thing to see is that the -NH₂ group, a nitrogen and two hydrogens, is replaced with an -OH group, an oxygen and a hydrogen.

In fact, niacinamide is so stable, that a 10% solution can be heated to 120 °C (248 °F) for 20 minutes with no niacin forming.

In another experiment it took about 75 hours in a pH 2 solution at 90 °C (194 °F)  to convert about half the niacinamide to niacin.

Heat vastly speeds up reactions; a rough approximation is that every 10 °C (18 °F)   increase in temperature doubles the reaction rate. If the pH 2 solution was kept at 30 °C (86 °F)   we could expect it to take over 4800 hours or almost half a year – and that’s if the acidic solution didn’t corrode your skin first!

An experiment with temperature conditions closer to room temperature shows how heat affects the rate of conversion. Only after 6 weeks of storage at 45  °C (113 °F) in acidic pHs did they find niacin, and the conversion never exceeded 2%. At room temperature (25 °C or 77 °F) the amount of niacin was less than 1% after 6 weeks, but the measurement wasn’t accurate enough to tell exactly how much, just that a small amount was present.

Another thing to keep in mind is that reaction rates also slow down when the viscosity or thickness of the solution is increased. Most skin care products, even serums, are thickened to some extent – which will further slow down the conversion of niacinamide to niacin.

If we can get metaphorical for a second, chemical reactions aren’t like a distance race. They’re more like jumping over hurdles. There’s a minimum amount of energy that’s needed to cause the molecule to change, called the activation energy. If you don’t have the energy to jump over a hurdle, you can’t progress. You can’t just roll on the ground until you hit the finish line.

What all this means is that products formulated with niacinamide and an acid may produce some niacin over time. This can be a problem for some, as even a miniscule amount of niacin can produce some faint skin redness, as little as 0.001% – amounts in the range of 0.01% to 0.1% will produce much more apparent skin redness for more people.

It’s also important to note the difference between irritation due to an acidic product versus the flushing caused by niacin. Niacin flushing appears evenly, affecting everywhere it’s been applied. It is also temporary (often lasting longer than 20 minutes), and comes with a tingling sensation.

If you’re using a product with niacinamide and ascorbic acid in the ingredients list and aren’t noticing any skin reddening…there’s either very little niacin that’s been formed, or you’re not very sensitive. If you’re worried about a product that contains both ingredients, storing it in a cool environment will discourage transformation of niacinamide to niacin.

But what about applying a product with niacinamide and then one with ascorbic acid? Is niacin being formed? I don’t want to say absolutely not, but the amount potentially formed is so miniscule, I don’t think it’s a relevant worry.

Niacinamide and Vitamin C (Ascorbic Acid) Complex

Mixing niacinamide and ascorbic acid turns the two clear solutions a yellow colour, but this isn’t the same yellow colour that appears when ascorbic acid is oxidized into dehydroascorbic acid.

This yellow color is due to the formation of a charge-transfer complex, called niacinamide ascorbate. An electron is transferred from the ascorbic acid to the niacinamide – this weakly holds the two together.

I think the fear of this complex negating the benefits of both ascorbic acid and niacinamide is not knowing that this complex is easily reversed and separated.

An experiment found the association equilibrium, or the balance of free ascorbic acid and niacinamide to niacinamide ascorbate, to be 1.45 at 25 °C (77 °F) .

This experiment also found that the pH of the solution that the two are mixed together in affects how much of the niacinamide ascorbate is formed. Niacinamide ascorbate forms best at a pH close to 3.8, but at pHs higher or lower less is formed. This means if the pH of a solution they were mixed together in was changed, away from 3.8, the two molecules would separate from each other.

This means if we added the same number of molecules of niacinamide and ascorbic acid into a solution of pH 3.8, about half of them would be in the niacinamide ascorbate complex, and the rest of them would just be on their own floating around.

I’m going to do a separate post that will walk through the calculation of this.

The pH dependent formation is important, because only the surface of our skin is acidic. Each deeper layer of skin becomes less and less acidic, finally reaching physiological pH which is around 7. This means as the niacinamide ascorbate moves deeper into the skin, there’s less impetus for them to be associated with each other. As well, as more individual ascorbic acid and niacinamide molecules move into the skin, the ratio of free to complexed niacinamide and ascorbic acid would decrease, and the complexed niacinamide ascorbate would separate until equilibrium was reached again.

One study that used niacinamide ascorbate on human skin explants found that it was still able to reduce melanin production in response to UV exposure. So it would seem its active effects aren’t hampered by being complexed together.

Another experiment found that the niacinamide ascorbate complex helped stabilize the ascorbic acid against degradation.

So the important takeaway is to know that the yellow colour isn’t the same thing as an oxidation of ascorbic acid, and that the complex formed between niacinamide and ascorbic acid is completely reversible. The niacinamide and ascorbic acid are held together like two pieces of paper with static, versus glue.

There is one paper that is cited to say that UV exposure caused the production of hydrogen peroxide in the skin when niacinamide and ascorbic acid were used together, however the effect was small and the proposed peroxyl radical mechanism is theoretical.

Many skin care ingredients will degrade or change with UV exposure, but using a sunscreen will greatly reduce or even eliminate the chances of this occurring.

The paper also theorized that by mixing the niacinamide and ascorbic acid with tocopherol (Vitamin E), the radical production could be mitigated.

Takeaway

I hope this has helped you understand what’s occurring when you mix niacinamide and ascorbic acid (or any acid) together. While there are chemical reactions that occur, they either occur super slowly, or are reversible.

You can definitely still choose to use niacinamide and ascorbic acid separately. You could use ascorbic acid during the day and niacinamide in the evenings. If you do choose to use them together, I don’t think the evidence points to any disabling of their benefits or any skin damage.

People do often experience some redness or tingling when using the two, but I think that can be chalked up to the irritation caused by ascorbic acid, especially if the product isn’t pH adjusted and acidic. I don’t want to suggest you to take a niacin pill to experience a flush, but unless the redness is very even and demarcated, it’s not likely due
to niacin.

Thank you to Jonathon Moir and James LaFortune for their expertise and help in writing this article