Skincare Ingredients Explained: What They Are, How They Work and Who They're For
By Mary, founder of Reti Skin · Last updated 20/09/2026
The short answer: Skincare ingredients work in three main ways. Some exfoliate (acids), some signal your skin cells to renew (retinoids, peptides, niacinamide), and some protect or hydrate your barrier (vitamin C, hyaluronic acid, ceramides, SPF). What matters is the ingredient, how much is in the product, and whether it suits your skin.
Ingredient lists are often written to impress you rather than inform you. So here's what the most common ingredients actually do, in plain English.
Three questions to ask about any ingredient
- What is it?
- How does it work?
- How much is actually in there?
If a brand can't answer all three, be sceptical. I show real percentages on our products for exactly this reason.
Cleansing oils: why put oil on your face to clean it?
Because like dissolves like. Sebum, sunscreen and makeup are oil-based, so oil lifts them off better than water alone.
Jojoba is a popular choice because its structure is similar to your skin's own sebum. Our Remove Cleansing Oil Pads contain just over 31% jojoba oil and just over 31% sunflower seed oil [confirm this matches the pads' INCI].
Shop Remove Cleansing Oil Pads
Glycolic and lactic acid (AHAs)
Both are exfoliating acids. They loosen the "glue" between dead skin cells so they shed more easily.
- Glycolic acid is the smallest molecule, so it works faster and goes deeper. It's also the more likely to irritate.
- Lactic acid is larger and gentler, and it helps skin hold onto moisture.
Our Renew Chemical Peel Pads combine 5.2% glycolic acid and 4% lactic acid.
Shop the Renew Chemical Peel Pads
Salicylic acid (BHA)
Glycolic and lactic acid are water-soluble, so they work on the skin's surface. Salicylic acid is oil-soluble, so it can get inside pores and dissolve the mix of oil and dead skin that clogs them.
That's why it's a go-to for blackheads and congestion. It's also why it can be drying, so start slowly.
Azelaic acid
A naturally occurring acid found in grains like barley. It's studied for redness, uneven tone and breakouts, and it's generally well tolerated, which makes it a good option when other actives are too harsh.
Cosmetic products usually contain up to 10%. Higher strengths are prescription read the percentage details here
Niacinamide
Niacinamide is vitamin B3. It helps your skin make more of its own ceramides, the fats that hold your barrier together, so a stronger barrier means less water loss and less reactivity.
It's also studied for redness and uneven tone. read niacinamide benefits
Vitamin C
Vitamin C is an antioxidant. It neutralises the unstable molecules (free radicals) that UV and pollution create. It also plays a role in collagen production and can help fade dark spots.
The catch is that pure vitamin C (L-ascorbic acid) is unstable, so many formulas use gentler, more stable forms. Reti's Brighten Vitamin C Serum is coming soon!
Retinoids and bakuchiol
Retinoids tell skin cells to turn over faster and support collagen. They have decades of evidence behind them.
Bakuchiol is a plant-derived alternative that's gentler. The research is promising but much smaller. The honest version is that retinoids are stronger and bakuchiol is kinder.
Peptides
Peptides are short chains of amino acids that act like messages to your skin cells, nudging them to produce more collagen and support repair.
"Peptides" is a huge category. Some have solid evidence and others are mostly marketing. Ask which peptide it is, and how much is in there. Some are supplied in a carrier solution, so check whether the percentage refers to the peptide itself or the whole blend.
Hyaluronic acid
Hyaluronic acid is a humectant, meaning it attracts and holds water. It doesn't "plump" skin permanently. It draws moisture in, so it works best on damp skin and under a moisturiser that seals it in.
Ceramides
Think of your skin barrier as a brick wall. Skin cells are the bricks, and ceramides are the mortar holding them together. They make up roughly half of the fats in that barrier and your levels drop as you age.
Adding them back helps skin hold water and feel less reactive.
Sunscreen (zinc oxide and other filters)
The most proven anti-ageing product isn't a serum. Sunscreen filters protect skin from UV before it damages collagen and causes pigmentation.
Zinc oxide is a mineral filter that sits on top of skin. Chemical filters absorb UV and convert it to heat. The best one is the one you'll actually wear every day: broad-spectrum, SPF 50+, reapplied through the day. NZ's UV is strong, so this matters here. (read the importance of SPF in skincare)
Why the dose matters
An ingredient at 0.1% and at 5% are not the same product. But more isn't always better either, because stacking several strong actives is the fastest way to irritate your barrier. Formulation also matters: pH, the form of the ingredient and the rest of the formula all change how well it works.
Can you mix skincare ingredients?
Mostly, yes. The famous "never mix" rules are often overstated.
- Vitamin C and niacinamide: the "they cancel out" rumour traces back to an old study using high heat over long periods. In a normal routine they work fine together.
- Exfoliating acids and retinoids: the issue isn't chemistry, it's irritation. Alternate nights instead of stacking them.
- General rule: introduce one new active at a time, two weeks apart.
FAQ
What order should I apply skincare ingredients?
Generally thinnest to thickest: cleanse, then serums, then moisturiser, then SPF in the morning.
Which ingredients are best for beginners?
Niacinamide, hyaluronic acid, ceramides and SPF are the gentlest starting point. Add acids or retinoids slowly afterwards.
Do I need to use all of these?
No. Pick the ingredient that matches your main concern, and don't add more than your skin needs.
Is bakuchiol as good as retinol?
Not proven. It's a gentler option with promising but limited research.
Mary is the founder of Reti Skin, a New Zealand skincare brand that formulates with full ingredient transparency. This article is general education and not medical advice.
