The invention relates to methods for treating or preventing abnormal skin conditions in a human in need thereof, comprising administering a cell culture composition comprising a living culture of bacteria comprising at least one engineered strain that produces a recombinant polypeptide for therapeutic treatment of the abnormal skin condition. The invention also relates to pharmaceutical compositions containing, as the active principle, engineered microorganisms expressing non-vaccinogenic pharmacologically active recombinant therapeutic polypeptides in order to treat or prevent abnormal skin conditions.