These three turn up on most serum labels, often together, usually without much explanation. They do quite different jobs.
Niacinamide
A form of vitamin B3, and one of the better-studied cosmetic ingredients. It visibly evens tone and helps reduce the appearance of excess shine, which is why it appears in formulas aimed at very different skin types.
Its practical advantage is tolerance. Where many actives demand a slow introduction, niacinamide is comfortable for most people from the start. Typical cosmetic concentrations sit in the low single digits to around ten percent; higher is not obviously better and is more likely to feel warm on application.
Hyaluronic acid
A humectant — it holds water at the surface so skin looks plumper and more even. Despite the name it is not an exfoliating acid and does nothing abrasive.
The detail worth knowing: humectants work with the water that is already there. On a dry face in dry air, a humectant has little to draw on. Apply it to skin that is still slightly damp from cleansing, and put something on top to slow that water leaving again. Without the second step it is largely evaporation.
Glycerin does much the same job and is often in the same formula. It is less fashionable and no less effective.
Peptides
Short chains of amino acids, included in cosmetic formulas for the look of firmness and smoothness over time. Palmitoyl tripeptide-5 is the one in our HA Serum with Peptides.
Peptides are the slowest of the three to show anything. Where niacinamide can visibly affect shine within weeks, peptides are a matter of months, and the change is subtle. They are worth including and not worth expecting drama from.
Do they work together?
Yes. The old warnings about niacinamide clashing with other ingredients came largely from a misreading of laboratory conditions unlike anything in a finished formula. A serum containing all three is normal and sensible.
What actually causes trouble is stacking several strong actives from different bottles — an acid, a retinoid and a vitamin C in the same routine — and then wondering why skin feels worse. That is a quantity problem, not a chemistry one.
Where they sit
After cleansing, before moisturiser, on skin still slightly damp. A serum is a delivery step, not a finishing one: it needs something over it. The 24/7 Barrier Cream does that job here.
Eight ingredients is the whole of our serum, by deliberate restraint. A short list makes it far easier to tell what your skin is responding to.
Percentages, and when to ignore them
Ingredient percentages are the most quoted and least useful number in skincare. A formula is a system: pH, delivery, what else is present and how it is stabilised all affect what a given percentage does on skin.
Ten percent niacinamide in a poorly built formula will not outperform five percent in a good one, and above roughly ten percent more people report a warm, flushed feeling with no visible advantage. Treat a very high number on the front of a bottle as a marketing decision rather than a specification.
What not to layer
The realistic failure mode is not two ingredients reacting in a jar. It is four active products in one routine, each recommended in isolation by someone who did not know what else you were using.
An exfoliating acid, a retinoid, a vitamin C and a strong niacinamide serum in the same week is a lot to ask of a face. If skin looks worse since you started a new routine, the most effective response is usually to subtract rather than add, give it a fortnight of the same three gentle steps, then reintroduce one thing.
Reading an ingredient list without a chemistry degree
Three habits get you most of the way. Look at the first five ingredients, since that is the bulk of the formula. Check what is missing — no synthetic fragrance and no drying alcohol near the top tells you more than any hero ingredient. And note the length: a short list is not automatically better, but it makes cause and effect far easier to establish when something does not agree with you.
What to expect, honestly
Hydration reads fastest — skin looks plumper and more even within days, because that is surface water. Tone takes weeks. The look of firmness takes months, if it comes at all.
Introduce one product at a time and photograph your face in the same light on day one and day thirty. Memory is a poor instrument for gradual change.
More on how the three steps fit together in our plain guide to barrier-first skincare, and on the step before this one in how to choose a gentle cleanser.
Cosmetic products are not intended to diagnose, treat, cure or prevent any condition.