What the research describes about skin ageing

Skin ageing comes from two sources. One is the clock, mostly genetic. The other is what your skin is exposed to.

The research is clear that ultraviolet light is the biggest outside factor. Its share of visible facial ageing is commonly put at around eighty percent.

Why does that split matter?

Because it tells you where to look. Compare sun-exposed and sun-protected skin on the same person, and studies describe very different rates of change in collagen, elastin and pigmentation.

It's the clearest natural experiment in the field, and it points at exposure, not your routine.

What do the sun protection trials show?

Randomised trials of daily broad-spectrum sun protection describe measurable differences in skin ageing over four to five years, compared with using it now and then.

The effect is preventive, not corrective. The trials measure slower change, not a reversal of what's already there.

Do sleep and alcohol show on your face?

Studies of short sleep describe changes people can spot in photos, like puffiness around the eyes and duller skin, after even one short night.

Alcohol affects skin through widened blood vessels and broken-up sleep. That makes the two hard to pull apart in observational studies.

How long before you see a change?

The outer layer of adult skin usually turns over in four to six weeks, and deeper layers take much longer. So ninety days is roughly two epidermal cycles: enough for surface changes, not structural ones.

The trials use photos under identical lighting, because the mirror is a poor tool for slow change.

When should you see someone?

Any new, changing or asymmetric spot is a question for a dermatologist. A routine doesn't cover it.