Needleless syringe operating with an impact wave generator through a wall

A needleless syringe for injecting an active principle, comprising:

• a propelling system including a shock wave generator device;
• an application guide for applying said syringe to the skin of the subject to be treated;
• and
• a resistant barrier which ensures an effective propagation of a shock wave through the resistant barrier, and is located entirely within the application guide, and comprises an upstream face and a downstream face, said downstream face having at least one blind cavity in which the active principle is accommodated, the resistant barrier remaining fixed within the syringe during injection, wherein the resistant barrier has a first position before injection and the first position is substantially maintained after injection;
• and
• wherein the shock wave generator device is configured to deliver a shock wave to the upstream face of the barrier.