A low-power atmospheric pressure plasma source, comprising a plasma-forming region for injection of a plasma-forming gas; an excitation region for injection of a source of reactive species downstream of the plasma-forming region; and a narrow converging plasma exit for producing a narrow plasma jet, the source being electrically decoupled from a substrate under treatment by the plasma jet. The present source may find applications for example for skin treatment, etching of skin cancer cells, detachment of cells, removal of skin pigmentation and deposition of temporary organic films.