The invention relates to a device for injecting a medium into or underneath the skin with a series of pressure pulses. The device includes a reservoir (1) for the medium, an application unit (10) to inject the medium into or under the skin, a hydraulic high-pressure pump (6) to pump the medium out of the reservoir (1) into the applicator unit (10), and an electronic control unit (11) that is suitable for regulating the applicator unit (10) such that the medium is injected with a series of pressure pulses into or underneath the skin.