Niacinamide, salicylic acid, retinol: what skincare actives actually do

Walk down any skincare aisle and you'll be promised the world by ingredients with intimidating names. Most of the real work, though, comes down to a fairly short list of "actives" — ingredients that genuinely change something in your skin, rather than just sitting on top of it. Here's what each of the big ones does, in plain terms, so you can tell which belong in your routine and which are just noise.

First, what "active" even means

An active is an ingredient with a proven effect on the skin — unclogging pores, fading pigment, supporting collagen, calming inflammation. The rest of a product (water, oils, thickeners, fragrance) is there to deliver and stabilise the actives or make the texture pleasant. You don't need many, and piling on more isn't better — the skill is matching one or two to what your skin actually needs, and using them consistently.

Salicylic acid (BHA)

An oil-soluble exfoliant that gets inside the pore and clears out the mix of oil and dead skin that causes blackheads, whiteheads and spots. Because it's oil-soluble, it suits oily and acne-prone skin especially well. Best for: clogged pores, breakouts, oily skin. Go gently — daily can be too much for some skin, so a few times a week is a sensible start.

Glycolic and lactic acid (AHAs)

Water-soluble exfoliants that work on the surface, loosening the glue between dead skin cells so they shed more evenly. The payoff is smoother texture and a brighter look, and over time some help with fine lines and uneven tone. Glycolic is the stronger, more penetrating one; lactic is gentler and slightly hydrating, which makes it friendlier for sensitive or drier skin. Best for: dullness, rough texture, uneven tone.

Retinoids (retinol, retinaldehyde, adapalene)

The closest thing skincare has to an all-rounder, and the most evidence-backed anti-ageing ingredient there is. Retinoids speed up cell turnover and, over months, nudge skin to behave younger — fewer clogged pores, smoother texture, softer fine lines, more even tone. They're the backbone of both acne and ageing routines. The catch is they can irritate at first (dryness, flaking, the "purge"), so start low and slow — a pea-sized amount a couple of nights a week, building up — and always pair with sunscreen, since they make skin more sun-sensitive. Best for: acne, fine lines, texture, tone. Not for use in pregnancy — check with a doctor.

Niacinamide (vitamin B3)

The quiet multitasker. It calms redness and inflammation, helps regulate oil, supports the skin barrier, and can soften the look of pores and uneven tone over time. It's gentle, plays well with almost everything, and is a sensible pick if your skin is reactive or you're not sure where to start. Best for: redness, oiliness, barrier support, sensitive skin.

Vitamin C

An antioxidant that brightens dull skin, helps fade pigment and post-spot marks, and defends against some of the daily damage from sun and pollution. It works best in the morning, layered under sunscreen, where the two complement each other. It can be finicky — some forms oxidise and lose potency — so a stable formula in opaque, air-tight packaging is worth seeking out. Best for: dullness, dark spots, daytime protection.

Hyaluronic acid

Worth clearing up, because the name confuses people: it's not an exfoliating acid at all. It's a humectant — a moisture magnet that draws water into the skin and plumps it, softening the look of fine lines that are really just dehydration. It hydrates but doesn't "treat" anything, so think of it as comfort and plumpness rather than correction. Best for: dehydration, plumpness, all skin types. Apply to slightly damp skin and seal with moisturiser.

Benzoyl peroxide and azelaic acid

Two more on the acne side. Benzoyl peroxide kills the bacteria involved in breakouts and reduces inflammation — effective, but it can be drying and bleaches fabric, so use a little and keep it off your nice towels. Azelaic acid is the gentle all-rounder of acne care: mildly antibacterial, anti-inflammatory, and good at fading the brown marks spots leave behind, while being well-tolerated by sensitive and rosacea-prone skin. Best for: breakouts (benzoyl peroxide), and breakouts plus marks and redness (azelaic acid).

How to actually combine them

A few simple rules keep you out of trouble. Introduce one active at a time, so you can tell what's helping and what's irritating. Don't layer multiple strong exfoliants, or a strong acid with a retinoid on the same night, while you're starting out — that's the fast track to an angry barrier. A reliable split is antioxidants (like vitamin C) and sunscreen in the morning, with your retinoid or exfoliant at night. And whatever you use, give it a fair, consistent run — most actives work over weeks to months, not days, and impatience is what makes people quit something that was actually working.

When to get advice

If your skin is persistently irritated, breaking out severely, or not responding despite a sensible routine, a pharmacist or dermatologist can point you to the right active or a prescription-strength option — and save you money on products that were never going to fix the problem.