Niacinamide, Hyaluronic Acid and Vitamin C: What the Evidence Says

Niacinamide, hyaluronic acid and vitamin C appear on almost every serum shelf, and the claims around them can get loud. This guide looks at what the research actually shows for each one, the concentrations used in studies, how to combine them, how to store vitamin C so it does not go off, and what results are realistic. None of these cosmetic ingredients cures a skin condition; if you are dealing with acne, melasma or rosacea, a dermatologist or pharmacist is the right first stop.

Niacinamide: a steady all-rounder

Niacinamide (also called nicotinamide) is a form of vitamin B3. The most widely cited clinical study, published by Bissett and colleagues in Dermatologic Surgery in 2005, had 50 women apply 5% niacinamide to one half of the face and a plain base to the other half, twice daily for 12 weeks. The niacinamide side showed reductions in fine lines and wrinkles, hyperpigmented spots, red blotchiness and sallowness (a yellowish tone), along with improved elasticity.

A 2021 review in the journal Antioxidants summarized the wider research: topical niacinamide, alone or combined with other ingredients, reduced the progression of skin aging signs and hyperpigmentation in clinical trials, and it was well tolerated by the skin.

Realistic take: niacinamide is a gentle, well-studied ingredient, and 5% is the strength behind the headline results. Higher percentages are not automatically better and can be more likely to irritate sensitive skin.

Hyaluronic acid: hydration, not magic

Hyaluronic acid is a humectant, meaning it attracts and holds water in the upper layers of the skin. That makes it especially welcome when indoor heating dries the air in a Canadian winter.

A 2011 study in the Journal of Drugs in Dermatology tested 0.1% hyaluronic acid creams made with five different molecular weights. Seventy-six women aged 30 to 60 applied them around the eyes twice daily for 60 days. All of the formulas significantly improved skin hydration and elasticity compared with placebo, but wrinkle depth improved significantly only with the two lowest molecular weights. It was a small study in one area of the face, so treat it as encouraging rather than conclusive.

Tip: apply hyaluronic acid to slightly damp skin, then follow with moisturizer to help keep that water where you want it. You do not need a high percentage; the study above used 0.1%.

Vitamin C: powerful but fussy

Vitamin C comes in two broad forms: pure L-ascorbic acid and more stable derivatives.

L-ascorbic acid

A 2013 review of vitamin C in dermatology explains that L-ascorbic acid stays stable at a pH below 3.5, and that a serum's efficacy rises with concentration only up to 20%; going higher does not add benefit. The same review reports that a combination of 15% vitamin C with 1% vitamin E and 0.5% ferulic acid increased vitamin C's efficacy eight-fold. Possible side effects include stinging, redness and dryness, which the review notes usually respond to moisturizers.

Derivatives

Ingredients such as magnesium ascorbyl phosphate, sodium ascorbyl phosphate and ascorbyl palmitate are more stable on the shelf. A 2017 review in Nutrients notes that phosphate derivatives can be converted to ascorbic acid in the skin, but slowly, and are poorly absorbed; it concludes that delivering vitamin C into the skin topically remains challenging. In short, derivatives are gentler and last longer, but the evidence for them is thinner.

Vitamin C is sometimes described as sun protection. It is not a sunscreen and never replaces a broad-spectrum SPF 30 or higher.

Combining them in one routine

First, a quick look at strengths used in research: 5% niacinamide in the key clinical study, 0.1% hyaluronic acid in the study above, and L-ascorbic acid with benefit levelling off at 20%. Lower strengths are a sensible start for sensitive skin.

You may have read that niacinamide and vitamin C cancel each other out. We have not found good clinical evidence that using them in the same routine is a problem, and many formulas contain both. The practical question is how your skin tolerates the mix.

• Morning: vitamin C serum, then hyaluronic acid or niacinamide, moisturizer and sunscreen.
• Night: niacinamide and hyaluronic acid pair easily with most routines, including retinol nights.
• If something stings, split them: vitamin C in the morning, niacinamide at night.
• Add one at a time, a few weeks apart, so you know which ingredient is doing what.

Apply thinner, watery serums first and creams last. Our Serums & Treatments and Moisturizers & Creams departments are organized to make that easy.

Storage and oxidation

L-ascorbic acid is unstable. The 2013 review notes that on exposure to light it oxidizes to dehydroascorbic acid, which turns it yellow, and that oxidized vitamin C can cause yellowish skin discolouration and stain clothes. To make a bottle last:

• Keep the cap tightly closed and store it away from light and heat, not on a sunny windowsill or beside a radiator.
• Choose opaque or tinted packaging where you can.
• If a clear or pale serum turns noticeably yellow or darker, it has oxidized and is time to replace.

Niacinamide and hyaluronic acid are far less fussy, but normal cool, dry storage is still sensible.

Patch test and set realistic expectations

The American Academy of Dermatology's patch-test method is to apply a product to a quarter-sized spot, such as the underside of your arm or the bend of your elbow, twice a day for seven to 10 days. If a reaction appears, wash the product off, stop using it, and soothe the area with a cool compress or petroleum jelly if needed. See a dermatologist if a reaction is severe or does not improve.

As for timelines, the AAD notes that most skincare products take at least six weeks to show results, and sometimes up to three months. Expect gradual, modest change, not a transformation.

Serum checklist

• Niacinamide: gentle, evidence behind 5%, good for tone and texture.
• Hyaluronic acid: hydration and comfort; apply to damp skin and seal with moisturizer.
• Vitamin C: L-ascorbic acid up to 20% is the most studied; derivatives are more stable but less proven.
• Store vitamin C away from light and heat; replace it when it darkens.
• Patch test first, add one ingredient at a time, and give it six to 12 weeks.
• Always finish mornings with broad-spectrum SPF 30+.

Build the rest of your routine in our Skincare department.

Frequently asked questions

Can I use niacinamide and vitamin C together?

We have not found good clinical evidence that using them in the same routine is a problem, and many formulas contain both. If the combination stings, use vitamin C in the morning and niacinamide at night.

What percentage of niacinamide should I look for?

The most widely cited clinical study used 5% niacinamide twice daily for 12 weeks. Higher percentages are not automatically better and may irritate sensitive skin.

Is a higher vitamin C percentage more effective?

A 2013 review reports that vitamin C serum efficacy rises with concentration only up to 20%, so going higher does not add benefit. Lower strengths are a sensible start for sensitive skin.

How do I know if my vitamin C serum has oxidized?

L-ascorbic acid turns yellow as it oxidizes. If a clear or pale serum becomes noticeably yellow or darker, it is time to replace it, and storing it away from light and heat helps it last.

How long do niacinamide, hyaluronic acid and vitamin C take to work?

Hyaluronic acid can make skin feel more hydrated quickly, but the American Academy of Dermatology notes that most skincare products take at least six weeks to show results, and sometimes up to three months.