A prunella extract or at least a prunella saponin is used to prepare a cosmetic or pharmaceutical and/or dermatological composition. Said composition enables keratinocyte renewal and differentiation to be regulated and has an anti-ageing, anti-inflammatory (particularly in inflammations caused by ultraviolet radiation), anti-allergic or anti-free-radical activity. It also allows the epidermis of normal skin to be kept in good condition, in particular by maintaining the functional role of the skin, specifically as protective barrier, and can be used to prevent or treat dry skin, particularly ichthyotic skins, and to treat psoriasis.