Flea collars' effectiveness is arguable.
For organophosphate and carbonate based flea collars, the warnings include keeping the collar out of reach of children and not allowing them to play with it.
Of these, 99 related to organophosphorus sheep dips and 45 to other veterinary medicines, including mineral oil based vaccines, flea collars and pour-on products for dogs and cats.
People excepted from that are those such as farmers dipping twice a year or people who occasionally attach flea collars to cats or dogs.
Dog and cat flea collars are specially formulated to give a very slow, local release on to the surface of the animal.
Organophosphorus exposure from products such as fly strips and sprays and flea collars, when used in accordance with the label directions, is very low.
