Structural changes in ageing skin.

As average life expectancy is increasing, the ageing of skin presents a growing problem for dermatologists. When considering ageing it is important to distinguish between the effects of true biological ageing and environmental factors, such as exposure to sun. Epidermal changes associated with ageing involve the flattening of its underside, a reduction in the number of Langerhans cells and of melanocytes, and a decline in the number of melanosomes synthesized, leading to reduced pigmentation. Dermal changes involve a reduction in the collagenous and elastic fibres, fibroblasts, mast cells and macrophages, and dilation of the lymphatic channels. The number of hair follicles declines with age, but their structure remains unchanged. Ageing does not affect the sebaceous glands, but some changes occur in the exocrine sweat glands.