Aqueous parasiticidal suspension (S1) comprises at least 20 wt.% sodium bicarbonate. Independent claims are also included for: (1) controlling the growth of parasites on animals reared in buildings by contacting the animals' environment in the building with (S1), and (2) use of an aqueous suspension containing 1-15 wt.% silica and 30-45 wt.% sodium bicarbonate for its combined parasiticidal and antifungal effects. ACTIVITY : Antiparasitic; Acaricide; Insecticide. MECHANISM OF ACTION : None given.