Understanding skin ageing: intrinsic and extrinsic
Part of skin ageing is unavoidable; a substantial part is not. Knowing the difference makes it immediately clear which anti-aging promises are plausible — and which are not.
Almost any anti-aging promise can be placed with a single question: does it address the part of skin ageing that can actually be influenced? Anyone who has understood the difference between intrinsic and extrinsic ageing can tell within seconds which marketing claim might be plausible and which cannot. This article is the foundation on which many further pieces on this platform build.
Two processes running at the same time
Skin ageing is not a single process but the sum of two, and they differ fundamentally in how far they can be influenced [1].
Intrinsic ageing
The genetically determined, time-dependent component. It runs in every tissue of the body and cannot be halted. In the skin it appears as follows:
- The epidermis becomes thinner and cell renewal slows
- Production of collagen and elastin declines
- Sebum and sweat production fall, and the skin becomes drier
- Subcutaneous fat and bone structure change, and the face loses volume
Purely intrinsically aged skin — readily seen on body areas that receive little sun — is typically pale, thin and finely lined, but even in appearance.
Extrinsic ageing
The component caused by external influences. It is added to intrinsic ageing and is the reason why two people of the same age can look very different.
By far the most important factor is UV radiation, which is why this is also called photoageing. Alongside it, smoking, air pollution, lack of sleep, chronic stress and nutrition play a role — together summarised under the concept of the skin ageing exposome [2].
Sun-damaged skin looks different from skin aged only by time: leathery, unevenly pigmented, with coarser wrinkles, visible small vessels and enlarged pores.
| Intrinsic | Extrinsic | |
|---|---|---|
| Cause | Time, genetics | UV, smoking, environment, lifestyle |
| Can be influenced | Barely | Considerably |
| Appearance | Thin, finely lined, even | Leathery, blotchy, coarsely lined |
| Typical sites | Inner upper arm, buttocks | Face, neck, décolleté, backs of hands |
What happens at the cellular level
UV radiation acts through several routes. It generates reactive oxygen species that damage cell components. It simultaneously activates enzymes known as matrix metalloproteinases, which break collagen down. And it inhibits the formation of new collagen at the same time [3].
The result is a double deterioration in the balance: more breakdown alongside less build-up. Over years this accumulates into a measurable loss of structure — what becomes visible as laxity and wrinkling.
A substantial part of what is perceived as ageing is cumulative sun damage — and therefore avoidable.
What follows from this in practice
An order of priority follows directly from the mechanism. It regularly differs from the order suggested by advertising.
- Sun protection. The only measure for which a slowing of skin ageing has been shown in a randomised controlled trial [4]. It works preventively — so the benefit is greater the earlier it begins.
- Not smoking. Smoking measurably accelerates skin ageing and additionally impairs wound healing after aesthetic procedures.
- Topical retinoids. The only ingredient with a demonstrated structural effect on sun damage already present.
- Sleep, nutrition, stress. Plausible and supported by observational data, but less firmly established than the first three points.
- Aesthetic treatments. These can soften visible signs but do not change the underlying process.
The most important error in reasoning
Aesthetic treatments and anti-aging strategies are often lumped together. They do fundamentally different things.
A treatment changes the result — it smooths, fills, tightens. Prevention changes the course — it slows how quickly new damage arises. Both are legitimate, but one does not replace the other. Anyone having regular treatments while living without sun protection is working against themselves.
Assessment
The inconvenient conclusion: the most effective measures against premature skin ageing are unspectacular, inexpensive and have been known for decades. They are hard to market precisely because they are so simple. That is exactly why they receive so little space in advertising — and exactly why they come first here.
References
- Farage MA, Miller KW, Elsner P, Maibach HI. Intrinsic and extrinsic factors in skin ageing: a review. International Journal of Cosmetic Science, 2008.
- Krutmann J, Bouloc A, Sore G, Bernard BA, Passeron T. The skin aging exposome. Journal of Dermatological Science, 2017.
- Fisher GJ, Kang S, Varani J, et al. Mechanisms of photoaging and chronological skin aging. Archives of Dermatology, 2002.
- Hughes MC, Williams GM, Baker P, Green AC. Sunscreen and prevention of skin aging: a randomized trial. Annals of Internal Medicine, 2013.
Last reviewed: August 2026.