The present invention addresses the problem of providing: a novel peptide having a high medicinal effect and high efficacy； and a medicine and an external preparation, particularly a prophylactic or therapeutic agent for dermatitis, rhinitis and alopecia, a hair regrowth agent, a hair growth agent, an antipruritic agent, a skin care product and the like, each comprising the peptide. The present invention achieves the problem by providing a cyclic peptide, a derivative of the cyclic peptide or a pharmaceutically acceptable salt of the cyclic peptide or the derivative, wherein the cyclic peptide comprises the amino acid sequence represented by formula I and the amino acid sequence does not have a peptide bond between amino acid residues other than amino acid residues constituting the amino acid sequence.本發明的目的在於提供一種藥效、效能強的新胜肽，及含該胜肽的藥物或外用劑，尤其提供對於皮膚炎、鼻炎、禿髮症的預防或治療劑、或生髮劑、育髮劑、止癢劑、皮膚保養用品等。本發明提供一種環狀胜肽或其衍生物、或者該環狀胜肽或其衍生物的藥學上可容許的鹽，其具有式1所示的胺基酸序列，且該胺基酸序列不具有構成該胺基酸序列的胺基酸彼此以外的胜肽鍵，藉此達成上述目的。
