Acid exfoliants have a marketing problem. The word “acid” does a lot of unearned scaring, and the word “peel” does a lot of unearned promising. What’s actually happening is more ordinary than either implies. An AHA — alpha hydroxy acid — is a small, water-soluble molecule that loosens the bonds holding dead cells to the skin’s surface, so they shed a little more easily than they would left alone. That’s the mechanism. It’s worth understanding before you decide how, and how often, to use one.
What “leave-on” actually means
Most exfoliating acids on the market are rinse-off: a five-minute mask, or a toner you wipe on and move past. A leave-on formula is a different commitment. It stays on your skin for hours — overnight, in this case — which means it keeps working for far longer than a quick pass ever could, and it also means any irritation has longer to make itself known. Leave-on isn’t automatically gentler than rinse-off. It’s slower and more thorough, which is a different thing entirely, and it changes how carefully you should introduce it.
That’s exactly why the first night matters more than it would with a rinse-off product. Patch test before your first full application, not just the first time you’ve ever used any exfoliant — we’ve written up the proper way to do it in how to patch test a new skincare product.
Who should hold off
If your skin is currently reactive, flaking, or generally unhappy, an exfoliating acid is the wrong thing to add right now — not because the ingredient is unsafe, but because exfoliation is one of the most common things people are already overdoing without realising it, often stacked across a cleanser, a scrub and a retinoid at once. If any of that sounds familiar, we’ve written about the pattern and what to do about it first in 5 signs your skin barrier needs help. The short version: calm skin down before you reintroduce actives, and bring them back one at a time.
How to use ours
Our AHA Peeling Concentrate is built on 10% plant-derived lactic acid, with 1% hyaluronic acid added specifically to keep the experience comfortable rather than tight while the acid does its work. Lactic acid is generally considered one of the milder AHAs, which is part of why it suits a leave-on, overnight format in the first place rather than a short-contact peel.
Use it 1–2 times a week, in the evening. Apply to clean, dry skin and leave it on overnight — it isn’t rinsed off before bed. Mild tingling on first use is normal and expected; it isn’t a signal to stop, though genuine discomfort is. The texture is lightweight and turns slightly tacky as it sets on skin, which is just the formula doing what a leave-on exfoliant does, not residue you need to wipe away.
One instruction matters more than the rest: exfoliating acids increase your skin’s sensitivity to the sun, so wear SPF the next morning. That’s true of any AHA, ours included, and it’s the one part of this routine that isn’t optional.
What’s actually in the bottle
Beyond the 10% lactic acid and 1% hyaluronic acid, the formula also carries sage and white tea leaf extract. It’s certified natural, vegan, and made in the EU. One thing worth knowing before you buy: it isn’t fragrance-free. There’s a light, naturally sweet scent, and there’s currently no allergen listed on the label. If you’re avoiding fragrance specifically, that’s worth knowing now rather than on first use.
Reading the label yourself
A “10%” figure on a product page is a specific, checkable claim, and it’s fair to want to know how it stacks up against everything else in the formula. If you want the general mechanics of how ingredient lists are actually ordered — and which front-of-box words are audited versus decorative — we’ve laid that out separately in reading a skincare label: what to actually check.
Why lactic acid, specifically
The AHA family covers several different acids, and they’re not interchangeable — glycolic acid has the smallest molecule of the common ones and tends to penetrate fastest, which is part of why it’s associated with stronger, quicker effects and a higher chance of irritation. Lactic acid’s molecule is larger, so it tends to work a little more gradually, and it carries the added property of drawing moisture to itself, which is one reason it’s commonly paired with a humectant like hyaluronic acid in leave-on formats rather than left to work alone. None of that is a claim about our specific formula beyond what’s already stated above — it’s simply why lactic acid, rather than a different acid, tends to be the one chosen for an overnight, leave-on approach in the first place.
Can You Use an AHA With Other Actives?
This is where a lot of over-exfoliation actually starts — not from the AHA itself, but from stacking it with everything else in a routine on the same night. If you’re also using a vitamin-C serum, alternate nights rather than layering both at once; combining an acid exfoliant with a strongly acidic vitamin-C formula on the same evening tends to increase irritation without adding a proportional benefit. The same goes for a retinoid: exfoliating acids and retinoids both increase skin’s sensitivity and turnover, and using them on the same night is one of the most common ways people end up with irritation neither product would have caused on its own. A simple, workable pattern many people land on: AHA on some evenings, other actives on others, rather than a routine where every ingredient goes on every night.
How Long Before You Notice a Difference?
Exfoliation is a gradual, cumulative process, not an overnight one. Most people using a leave-on AHA one to two times a week notice a difference in overall texture and evenness over several weeks of consistent use, not after one or two applications. Judging it too early is one of the more common reasons people give up on a genuinely well-suited product — or, in the opposite direction, increase frequency too soon because “nothing seems to be happening yet,” which is exactly the pattern that leads to over-exfoliation instead of the improvement they were hoping to speed up.
AHA Exfoliant vs. a Physical Scrub
These solve the same broad problem — helping dead skin cells shed — through genuinely different mechanisms, and they’re not interchangeable. A physical scrub relies on friction: granules or a textured tool manually dislodging cells from the surface. An AHA works chemically, loosening the bonds between cells without any manual abrasion at all. A scrub’s effect stops the moment you rinse it off; a leave-on AHA continues working for as long as it stays on skin. For most skin types, especially anything reactive or sensitive, a chemical exfoliant is the gentler route to the same result, because it isn’t adding physical friction to skin that’s already sensitive to over-exfoliation, whichever method causes it.
Common mistakes with a leave-on acid
- Applying it to damp skin. The instructions say clean, dry skin for a reason — applying an acid to a wet face changes how evenly it sits and can make the tingling stronger than it needs to be.
- Skipping SPF the next day because “it’s just one morning.” Increased sun sensitivity from an AHA doesn’t switch off after a single missed application — treat the next morning’s SPF as part of the routine, not an optional extra.
- Stacking it with another exfoliating step the same night. A leave-on acid left on overnight is already a thorough exfoliating step on its own. Adding a physical scrub, a separate acid toner, or a retinoid on the same evening is a common way people end up over-exfoliating without meaning to.
- Increasing frequency because the first week went fine. 1–2 times a week is the guidance for a reason; going straight to nightly use is the single fastest way to turn a comfortable routine into an uncomfortable one.
What we’d recommend
An exfoliating step doesn’t replace anything else in your routine — it sits alongside your normal cleanse, on the evenings you use it, and everything else carries on as usual the next morning (with SPF). If you want a gentle, honestly-labelled way into leave-on exfoliation rather than a harsher rinse-off peel, the AHA Peeling Concentrate is built to be used twice a week at most, comfortable rather than tight thanks to the hyaluronic acid sitting alongside the acid, and it’s certified natural and made in the EU. Start at once a week, watch how your skin responds over a couple of applications, and only move to twice a week once you know it agrees with you. Pair it with a fragrance-free moisturiser the next morning if your skin runs reactive — ours is built to calm redness-prone skin while the acid finishes its work overnight.
Quick Answers
How often should I use an AHA exfoliant?
1–2 times a week for a leave-on formula like this one. Going higher doesn’t speed up results — it’s the most common route to irritation.
Can I use an AHA every night?
Not recommended for a leave-on, overnight formula. Nightly use is far more likely to over-exfoliate than to accelerate results — stick to the 1–2 times a week guidance and give your skin the rest of the week to recover in between.
Should I exfoliate in the morning or at night?
At night, for a leave-on AHA specifically — it’s designed to stay on while you sleep, and exfoliating acids increase sun sensitivity, so applying one in the morning right before sun exposure isn’t the ideal timing regardless of formula.
