Eine schnelle und schmerzlose in-vivo-Analyse und eine Kommunikation der Ergebnisse mit Produktempfehlungen ist möglich durch ein Verfahren zur individualisierten Hautbehandlung, bei dem man im Rahmen einer in-vivo-Analyse den mittleren Fragmentierungsindex (mean fragmentation index A) der Bindegewebsfasern der papillären Dermis mißt, den Ist-Wert der Größe mit vorgegebenen Sollwerten vergleicht und die Haut des Individuums mit kosmetischen Mitteln behandelt, die den mittleren Fragmentierungsindex (mean fragmentation index A) der Bindegewebsfasern der papillären Dermis beeinflussen.Individualized skin treatment comprises (a) measuring an average fragmentation index (mean fragmentation index A) of the connective tissue fibers of the papillary dermis during in-vivo analysis, (b) comparing the actual value of the magnitude with predetermined target values and (c) treating the skin of the individual with cosmetic agents, which influence the average fragmentation index of the connective tissue fibers of the papillary dermis. Independent claims are also included for: (1) the efficiency evaluation of a skin cosmetic product, comprising (i) measuring the average fragmentation index of the connective tissue fibers of the papillary dermis of the untreated skin area during in-vivo analysis, (ii) cosmetically treating the skin area with the topically applied skin cosmetic product, (iii) measuring the average fragmentation index of the connective tissue fibers of the papillary dermis of the henceforth treated skin area during in-vivo analysis, (iv) comparing the value obtained from the step (i) with the values obtained from the step (iii), and (v) the evaluating the efficiency of the skin cosmetic product based on the influence on the average fragmentation index of the connective tissue fibers of the papillary dermis and (2) the age-determination of people, comprising (ai) measuring the average fragmentation index of the connective tissue fibers of the papillary dermis during in
