ABSTRACT
Background: Human hair follicle experiments cyclical transformations throughout its life. These are rest (telogen phase), growth (anagen phase) and regression mediated by apoptosis (catagen). During summer the percentage of telogen increases and the percentage of anagen decreases. Aim: To determine the seasonal changes of scalp hair follicle phases among Chilean subjects. Material and methods: Retrospective analysis of 514 differential trichograms of normal scalps from subjects aged 36±14 years, obtained between 1998 and 2008. Results: During summer and winter, the mean percentage of telogen was 20 percent±10 percent and 16 percent±10 percent, respectively (p <0.01). The figures for anagen in the same periods were 80 percent±10 percent and 83 percent±10 percent, respectively. Conclusions: This study confirms the presence of seasonal variations in normal trichogram.
