A post-mix drink dispenser includes a mixer body securable to a drink dispensing system and having at least one beverage concentrate inlet and outlet sheltered within a downwardly open cavity in the bottom thereof; a diluent channel formed exterior to the cavity and about a lower sidewall of the mixer body; and a nozzle housing securable in place about the mixer body. The dispenser includes an air channel formed in a wall portion of the nozzle housing, a diffuser to organize flows of diluent along the interior surface of the nozzle housing, or both a vent and a diffuser. The air channel includes provisions to impede ingress of diluent, and to contain flow through the channel of liquid beverage components. The diffuser may be formed unitary with the nozzle housing, or may be selectively removable from the drink dispenser.