There is described an application unit (12, 12') for applying an adhesive onto labels (2) to be applied to respective articles (3), comprising: an adhesive roller (20), which is rotatable about a first axis (C) and is adapted to receive an adhesive and to apply adhesive to said labels (2); an adhesive distributor (22), which is adapted to dispense adhesive on a surface (21) of said roller (20); an adhesive scraper (23), which is adapted to be arranged at a radial distance from surface (21), so as to remove an excess of adhesive from said roller (20) and to define the amount of said adhesive to be applied to labels (2); and adjusting means (24, 40) for adjusting the amount of adhesive to be applied to labels (2); adjusting means (24, 40) comprise an actuator (40), which is controllable to exert an adjustable force (F3) on adhesive scraper (23) also on the basis of at least one first operative parameter of said adhesive and/or labels (2) and/or said adhesive roller (20), so as to correspondingly adjust the pressure exerted by adhesive scraper (23) onto adhesive and correspondingly adjust the pressure exerted by said adhesive scraper (23) onto said adhesive and adjust said amount of said adhesive to be applied to said labels (2). (Figure 2)