Ageing across the life span: time to think again.

Living organisms are subject to ageing. This natural process has gained greater importance in socially and medically affluent societies. For many, ageing connotes unattractive changes in the appearance of the skin. The gross morphological changes of ageing skin are mirrored by a range of more profound age-associated physiological declines. Thus, skin ageing can be put into other perspectives which lie at the interfaces of molecular biology, cellular biology, oncology and cosmetic dermatology. Genetically programmed replicative senescence and stress-induced premature senescence (SIPS) are two processes that are fundamental to skin ageing. Some iteroparous species can be used as animal models for human ageing. Undoubtedly, scientific understanding of skin ageing is firmly rooted in the distinction between intrinsic and extrinsic types of ageing. However, seven major types of skin ageing can be distinguished: genetic, chronological, solar, behavioural, endocrinological, catabolic and gravitational types. Preventative measures can target each of these.