To increase a tissue regeneration ability of a living body such as a collagens production ability of fibroblast in the dermis in a skin defect area typified by a large wrinkle or wound, a flavanone derivative such as farrerol is used as an active ingredient of an external preparation for skin. Further, to efficiently screen a substance having an excellent effect on promoting wound healing, the remodeling action of collagen fiber bundle is tested by using skin wound model.
