A soothing cosmetic or pharmaceutical composition that includes at least one peptide that activates human HMG-CoA reductase general formula (I): R1-(AA)n-X1-Gly-Glu-Leu-Ser-X2-X3-(AAp-R2 in a physiologically suitable medium is disclosed. The invention further applies to a cosmetic treatment method intended to combat skin irritations. Additionally, methods of treating skin irritations with such a composition are described.