If resistance to Frontline could be demonstrated, all the other drug companies who make rival products would sing it from the rooftops. They can’t because there is no evidence. Flea numbers have increased in recent years for a number of reasons, climate included. Most failures are down to a build up of other lifecycle stages in the dog’s home environment.
The problem rarely admitted is they are not actually safe, or tested for long term useslightly off topic but if we can effectively treat our dogs with oral or spot om type products why can't we do the same for ourselves? If these type of products are deemed safe enough for our canine companions and millions of farm animals that go into the food chain they surely they should be safe enough for humans?