Age-related regional variations of human skin blood flow response to histamine

The process of ageing involves many changes in the skin. These changes are not necessarily uniform, so the pattern of regional variations may vary with ageing. The aim of the present study was to assess age-related regional variations in skin function, by measuring the cutaneous microvascular response to histamine. Histamine was topically applied to the back and forearm of a young and an aged group of volunteers (n = 28, 14 in each group), and the response was quantified utilizing laser Doppler flowmetry. The following parameters were calculated from the data and compared between the two groups: (i) peak response; (ii) the time required to reach the peak; (iii) the time required to decay to half the peak flow; and (iv) the area under the response time curve. For the young group, the magnitude of the maximum response, as well as the extent of the response as measured by the area under the response curve, were significantly greater on the back than on the forearm (p < 0.01 and p < 0.05, respectively). In contrast, for the aged group, the two sites did not significantly differ from each other. The time required to reach the peak was longer in the aged group over both sites, and so was the time required to decay to half the peak flow. These observations indicate regional anatomical or functional differences between old and young skin, which may provide insight into inherent differences influencing cutaneous manifestations of endogenous and exogenous diseases in various age groups.