The present invention is aimed at providing a novel peptide with quick expression of drug efficacy/effect and long duration of maintaining amelioration, a medicament or an external preparation comprising the same, in particular a prophylactic or therapeutic for dermatitis, skin roughness, rhinitis, alopecia or thinning hair, or a hair growth stimulant, hair growing agent, an antipruritic or a skin-care product, etc. The present invention has reached said object by providing a cyclic peptide having an amino acid sequence expressed by the formula I or a derivative thereof or a pharmaceutically acceptable salt thereof, wherein the amino acid sequence has no peptide bond other than those which are formed between the amino acids constituting the amino acid sequence.
