Line up ten faces of the same age and they will wrinkle at different rates. This is because two forces are at work, and only one of them is the calendar. Of course, the first is intrinsic ageing, the steady internal slowdown that everyone shares. Collagen and elastin production falls, and the skin makes less of its own oil and holds less water. Dead cells also linger longer at the surface. As a result, the skin grows thinner, drier and quicker to crease.
The second force is the one you can actually influence, and it does most of the visible damage. Sunlight is the biggest single culprit. Ultraviolet light breaks down collagen and elastin directly. This is a process called photoageing. It accounts for a large share of the lines people put down to age alone. The NHS guidance on sunscreen and sun safety is the plainest summary of why daily protection matters. Also, smoking narrows the vessels that feed the skin and adds its own fine lines around the mouth. Then, sugar stiffens collagen through a process called glycation. Meanwhile, dehydration, stress and years of the same expressions gradually etch dynamic lines into permanent ones. This is why a considered medical-grade skincare routine, built around SPF and antioxidants, matters. It protects any in-clinic result you go on to have.