Later than you are being told. In your twenties the structural changes that make a face look older — bone remodelling, fat-pad descent, ligament laxity — have barely begun. Most people in this decade are shown a problem that is not there yet, and the useful work is protective rather than corrective.
Not much is changing yet, and that is not a reason to intervene early. It is a reason to protect what you have and get your barrier working.
This is the decade with the widest gap between what is happening to a face and what that face is being sold, and the gap is not an accident. Twenty-somethings are the most reachable audience there is, and the industry has worked out that prevention is a story you can sell to someone with nothing wrong with them.
Collagen production has started its slow decline. It peaks in the early twenties and falls gradually from there — the commonly cited figure is around one per cent a year. That is real, and it is also so slow that it is invisible over this decade.
Sun damage is accumulating and is not yet visible. This is the important one. The pigmentation and texture people treat in their forties was mostly acquired before thirty. What you do about sun now is the single highest-return decision on this page, and it produces no visible result for twenty years, which is why almost nobody does it.
Oil production is often still high, and the hormonal patterns of the late teens can persist well into this decade.
Structurally: almost nothing. The bone has not receded meaningfully. The fat pads have not descended. The face you have is the face you have.
Rarely ageing. Usually one of these:
A damaged barrier from doing too much. By a distance the most common. Actives layered on actives, a routine assembled from short videos, skin that has become reactive and is then treated as sensitive — so it gets more products, and gets worse. The fix is subtraction, and it is free.
Acne, or what is left of it. A real thing, and often a medical question rather than an aesthetic one. Persistent or scarring acne belongs with a GP or a dermatologist, and anyone who treats it purely as a skincare problem is not helping.
Texture and marks left behind by picking. Also real, also mostly worked on by stopping.
Anxiety produced by photographs. A camera flattens depth and exaggerates whatever is nearest the lens. A great many people arrive concerned about something that is a focal length.
Prevention is a legitimate idea. "Preventative treatment" mostly is not.
The two get deliberately blurred. Preventing damage — sun, barrier, sleep, not smoking — is genuinely the highest-value thing available in this decade and almost none of it happens in a clinic. Treating a face pre-emptively for something that has not started is a different proposition wearing the same word, and the second one is what gets sold.
If someone your age is being told to start now so it does not get worse later, the question worth asking is: what specifically is changing, and what would it look like in five years if I did nothing? A good answer to that exists sometimes. If the answer is vague, the recommendation is too.
Sun protection, seriously and daily. A routine with fewer things in it than you currently have. Sleep, which does more than any serum in this decade. And a consultation if something specific is bothering you — with the understanding that "nothing yet" is a common and legitimate outcome.
Anything medical goes to your GP. Persistent acne, anything painful, anything changing quickly. A skin clinic is not the right room for those.
The three processes driving facial ageing — bone, fat and support — are described in your face is changing shape, not just texture. In your twenties all three have barely started, which is precisely why this decade's honest advice is so short.
A consultation is $150 and takes an hour. In this decade it is more often a conversation about what to stop doing than what to start, and that is a real outcome rather than a wasted appointment.