Depending on the active ingredient, it's difficult to say, but presumably the one you are referring to is
2,4-dichlorophenoxyacetic acidMost weedkillers target the plant metabolism rather than animal but my take on any weedkiller is that you treat it as a poison anyway, after all it is there to kill something - so take precautions and avoid exposure. I always wear gloves (like marigolds) and wash my hands immediately after using and definitely if I had come into contact, and yes, I suppose changing footwear would be a good idea too so that you didn't tread it into the house. When I used to use feed and weed (the previous owner thought the mass of yellow dandelions was so pretty when she was showing me the house LOL), I wouldn't allow the dog on the treated part of the lawn until a good amount of time had passed and after rain or heavy watering in had occurred to allow it time to degrade.
Spreckly wrote:We have a long, narrow back garden, with loads of growing plantains, daisies, and other weed, and I just thought we could treat it bit by bit.
Probably the best way - cordon it off (use some netting on canes) so that no-one or animal will accidentally walk on it.
I'm surprised you are having difficulty getting rid of plantains as there were a few growing on my plot recently and they didn't seem that difficult to dig up.