Functional and physiological characteristics of the aging skin.

As life expectancy in the U.S. increases - and with it the proportion of the aged in the population - appropriate care of elderly skin becomes a medical concern of increasing importance. As skin ages, the intrinsic structural changes that are a natural consequence of passing time are inevitably followed by subsequent physiological changes that affect the skin's ability to function as the interface between internal and external environments. The pH of the skin surface increases with age, increasing its susceptibility to infection. Neurosensory perception of superficial pain is diminished both in intensity and speed of perception (increasing the risk of thermal injury); deep tissue pain, however, may be enhanced. A decline in lipid content as the skin ages inhibits the permeability of nonlipophilic compounds, reducing the efficacy of some topical medications. Allergic and irritant reactions are blunted, as is the inflammatory response, compromising the ability of the aged skin to affect wound repair. These functional impairments (although a predictable consequence of intrinsic structural changes) have the potential to cause significant morbidity in the elderly patient and may, as well, be greatly exacerbated by extrinsic factors like photodamage. As numbers of the elderly increase, medical as well as cosmetic dermatological interventions will be necessary to optimize the quality of life for this segment of the population.