Flea & Tick Prevention > Collars, Preventic Amitraz Tick Collar for Dogs kills and detaches ticks. When the collar is worn, prevention lasts for up to three months. Preventic Tick Collars prevent new ticks from attaching and feeding within 48 hours after application. Fits dogs of almost any size. Over 97% effectiveness against ticks for up to three months. Does not kill or control flea populations. Cannot be used for cats. Water resistant and safe when used as directed.