The invention relates to a method for determining hair cycle markers in vitro, test kits and biochips which are used to determine hair cycle markers and to the use of proteins, mRNA molecules, proteins or fragments thereof as hair cycle markers. The invention also relates to a test method which is used to detect the effectiveness of cosmetic and pharmaceutical active ingredients which influence the hair cycle, in addition to a screening method which is used to identify cosmetic or pharmaceutical active ingredients which influence the hair cycle and to a method for the production of a cosmetic and pharmaceutical preparation which influences the hair cycle.