I do use it on my dog because of ticks.Very interesting. Fipronil is still very much used here for cats and dogs. There was a Fipronil contaminated egg scandal a few years ago which concerned many European countries...in France, the main problem laying hens commercial structures have is bioresistance to permethrin, since it was one of the only authorized product for laying hens. Bioresistance is an unavoidable evolution at some point if only one molecule is used; it is the ability of living organisms to adapt to stay alive.
Article on sulfur in commercial poultry house
http://entomologytoday.org/2016/07/18/battling-chicken-mites-with-bags-of-brimstone/