A compound of formula (I) R1-Wm-Xn-AA1-AA2-AA3-AA4-AA5-AA6-AA7-AA8-AA9-Yp-Zq-R2 wherein AA1 is Phe; AA2 is Trp; AA3 is selected from the group consisting of Met, Leu and lie; AA4 is selected from the group consisting of Lys, Arg and Gin; AA5 is Arg; AA6 is Lys; AA7 is selected from the group consisting of Arg, Lys and His; AA8 is selected from the group consisting of Val, lie, Leu and Met; and AA9 is Pro, useful in the treatment and/or care of the skin, hair, nails and/or mucous membranes, in particular for improving the barrier function of the skin, for energising the skin and as an anti- aging agent.