you should never use more than once a month. frontline is waterproof and will not come off. my vet has told me to even take my yorkie off frontline for january and feb so his body can have a rest from it. but i also live in cold climate and ground is frozen during those months. my vet also told me that k9 advantix is not good for little dogs as they also get upset stomachs when using it. most do not do well. really made for big dogs. hpefully my vet knows what he is talking about
