A dispenser for foamed detergents includes a cylinder (C) in which a piston (P) airtightly slides, the cylinder (C) being connected through a valve (V) to a foamer (F) where the detergent is mixed with air to form the foam which is dispensed through a dispensing chamber (U) provided with a nozzle (N), and further includes an additional piston (S) connected to the piston (P) through a shaft (A) and airtightly sliding in an additional cylinder (C'') in communication with the outside through a one-way valve (Y), a duct (D) extending between said additional cylinder (C'') and the dispensing chamber (U). In this way there is obtained the delivery of air through the duct (D) during the return travel to achieve the cleaning of the dispensing chamber (U) and of the dispensing nozzle (N) so as to prevent dripping of the foam and the development of mildew in case of a long interval before the next use.