Smoker's face: the biology of aging ten years faster

Skin firmness comes from collagen and elastin. Tobacco smoke boosts enzymes called matrix metalloproteinases that break collagen down, while simultaneously reducing new collagen production.

The result is subtraction on both sides of the equation: you destroy more and build less. Studies in identical twins where one smoked show visibly greater sagging, deeper wrinkles and more pronounced under-eye bags in the smoking twin.

Nicotine constricts the tiny vessels feeding the dermis, and carbon monoxide displaces oxygen in the blood that does arrive. Skin is left chronically underfed.

That produces the characteristic dull, greyish or sallow complexion, plus slower turnover of skin cells. Uneven pigmentation and a leathery texture follow with years of exposure.

Two mechanical habits carve their own lines: pursing lips around a cigarette creates vertical perioral wrinkles, and squinting through smoke deepens crow's feet.

Combined with collagen loss, this gives the recognizable pattern of prominent lines radiating from the lips and eyes, gaunt features and sunken cheeks.

Skin that heals badly is a real medical problem. Smoking impairs wound healing so much that plastic and orthopedic surgeons frequently require weeks of abstinence before elective procedures: skin flaps and grafts die more often in smokers.

Smoking is also linked to worse psoriasis, hidradenitis suppurativa and delayed healing of ordinary cuts.

Circulation to the skin improves within weeks, which is why many people are told they look better a month or two after quitting: better colour, better oxygenation, less puffiness.

Existing deep wrinkles do not disappear, but the accelerated destruction stops and the skin's repair machinery starts working normally again. From that point you age at the same speed as everyone else instead of faster.