The present invention addresses the problem of providing: a novel peptide which can exert the medicinal effect or efficacy thereof rapidly and has a long duration of remission； and a medicine and an external preparation, particularly a prophylactic or therapeutic agent for dermatitis, rough skin, rhinitis, alopecia or thinning hair, a hair growth agent, an anti-depilation agent, an antipruritic agent, a skin care product and the like, each of which contains the peptide. According to the present invention, the problem can be solved by providing a cyclic peptide comprising the amino acid sequence represented by formula I wherein the amino acid sequence does not contain a peptide bond other than peptide bonds formed between amino acid residues that constitute the amino acid sequence, or a derivative of the cyclic peptide, or a pharmaceutically acceptable salt of the cyclic peptide or the derivative.本發明的目的是提供一種藥效、效能的效果發現快，緩解維持期長的新型胜肽，包含此的醫藥或外用劑，特別是對於皮膚炎、皮膚刺激、鼻炎、脫髮症、毛髮稀疏的預防或治療劑或發毛劑、生髮劑、止癢劑、護膚用品等。本發明藉由提供一種環狀胜肽或其衍生物或藥學上可容許這些的鹽，以達成上述目的，其中該環狀胜肽具有以式I表示的胺基酸序列，該胺基酸序列不具有構成該胺基酸序列的胺基酸以外的肽鍵。
