AHA vs Retinol
AHAs work on the surface. They loosen the glue between dead cells, so skin looks smoother and brighter within a few weeks. Retinol works inside the cell, changing how your skin builds itself, so it does more for fine lines and pigment. The trade is time: an AHA shows something in a month, and retinol takes three to six.
What you do
A toner, serum, lotion or pad left on the skin. Some people use a stronger peel in a clinic every few weeks instead.
A pea-sized amount on dry skin at night, then moisturizer. Two or three nights a week at first, building up.
What you will see
Softer texture, less dullness, smaller-looking pores, and a slow fade of surface discolouration.
Fine lines soften, tone evens out, and acne-prone skin clogs less. It builds collagen, which nothing on the surface can do.
What it is best at
Rough patches, flaky skin, a dull surface, and the general look of skin that needs a reset.
The best-studied ingredient for photoaged skin. It also works on blackheads and post-acne marks at the same time.
How long until it works
Brightness comes quickly. Discolouration takes a few months.
Texture usually improves first. Lines and pigment are the slowest things it changes.
How long you use it
It is maintenance. Skin returns to its usual turnover a few weeks after stopping.
There is no course to finish. Stopping means the skin drifts back to how it was over months.
The downside
It can sting on application, especially on freshly washed skin, and it needs sunscreen alongside it every day.
The first few weeks are the worst of it. Starting slowly and moisturizing well avoids most of that.
Cost
Drugstore serums and toners are cheap. A course of in-clinic peels costs considerably more.
A drugstore retinol and a luxury one contain the same molecule. Price mostly buys the texture of the cream and the packaging.
The at-home or drugstore version
Drugstore AHAs are the same molecules a clinic uses, at lower strength and a higher pH. They work slowly and without peeling. A clinic peel is the same acid turned up.
The prescription version is tretinoin, which is stronger and faster. Retinol is a weaker relative your skin has to convert before it works. It is a slower version of the same thing, not a different thing.
Top-down and bottom-up
AHAs work from the top down: They dissolve the bonds holding dead cells to the surface, so those cells lift away and the skin underneath looks fresher. Nothing about the deeper skin has changed.
Retinol works from the bottom up: It binds to receptors inside skin cells and changes what they do — faster turnover, more collagen, calmer pigment cells. That is why it takes months and why the change holds.
So they are not two versions of the same idea: One is housekeeping and the other is renovation.
Which one for which complaint
Choose an AHA for dullness, rough texture and flaking: It is the faster, more forgiving option, and it is the easier one to start with if you have never used an active.
Choose retinol for fine lines, sun damage and acne: It is the ingredient with the strongest evidence behind it for skin that has aged in the sun, and it treats spots and marks at the same time.
Choose retinol if you can only afford one thing: It does most of what an AHA does, plus a great deal an AHA cannot.
Using both without wrecking your skin
Same night is how people end up red and sore: Both work on the surface layer, and stacking them is the most common cause of a damaged barrier.
Alternate nights instead: Retinol two or three nights a week, AHA on one or two of the nights in between, and nothing at all on the rest.
Give the retinol priority when your skin is complaining: Drop the acid first. It is the one you can stop for a fortnight without losing progress.
Before you start either one
Introduce one active at a time and hold it for eight weeks before judging
Start two or three nights a week, not nightly, whichever you pick
Apply retinol to dry skin — damp skin drives more of it in and more irritation with it
Keep a plain moisturizer in the routine from the first night
Wear broad-spectrum sunscreen every morning with either one
Peeling is barrier damage, not progress; back off when you see it
