PROBLEM TO BE SOLVED: To provide an agent for shortening hair growth telogen or a hair loss preventing agent by screening for a substance determining an internality factor regulating the telogen of a hair growth cycle and inhibiting the activity or expression of the internality factor.SOLUTION: In the invention, FGF 18 inherent in a follicle is found to regulate the telogen of the growth cycle of hair, to allow a falling period to start, and further to prescribe a hair cycle domain. And disclosed is a method for making into a candidate for a hair growth telogen shortening agent, a hair loss preventing agent and a hair quality regulating agent by screening an FGF 18 activity inhibitor or an FGF 18 gene expression inhibitor. Further, disclosed are the hair growth telogen shortening agent, hair loss preventing agent and hair quality regulating agent containing the FGF 18 activity inhibitor and/or expression inhibitor such as the partial peptide of the FGF 18, an anti-FGF 18 antibody or the like as an active ingredient.
