Transdermal delivery peptides for the treatment of skin diseases and/or facilitation or enhancement of transdermal delivery of pharmaceutically active agents are provided. Compositions comprising the transdermal delivery peptides and methods of therapeutic use, including the improvement of transdermal delivery of drugs or other pharmaceutically active agents, are also disclosed. Nucleic acids, expression vectors, and methods of their use, which encode the transdermal delivery peptides are disclosed. Methods are also provided for in vivo phage display for identifying further peptides with enhanced transdermal delivery capability.