It's true that fleas can develop a tolerance to various types of chemicals that have been used over a period of time in a particular area. It could be that is what is happening to the fleas in areas where Frontline has been used for several years.
They say these are prehistoric creatures that have adapted to all kinds of conditions for thousands of years. That is why Advantage came out with a new topical a couple of years ago called Advantage II although I think it is really III or IV. |