Frontline for Dogs not effective?

Our customer asked::

I have two seven year old terriers who are currently plagued by fleas. We've always used frontline drops and Acclaim environmental spray, which has worked well in the past. This year however, the treatments seem ineffective, as both dogs are scratching, rubbing and chewing out clumps of fur
Can I re-spray the house with acclaim even though it was only sprayed 3 months ago? and can I increase the frequency of the Frontline treatment to monthly on a regular basis, or is that risking overdose?

Our reply:

It has been a particularly bad year for fleas and lots of people are having a similar experience. It seems that it is still effective to use Frontline for dogs against fleas, but it is not able to kill every flea which jumps onto a dog before it has had a chance to feed a few times. In most years, when the flea population is not too great, Frontline is perfectly adequate. If the background flea population gets too high, then it takes a while to get under control and the fleas continue to be a nuisance for a while.

It is perfectly safe for you to repeat the Acclaim treatment again. You should keep animals out of the room when spraying. Then leave doors and windows closed and let the spray settle to the floor for an hour or two before going back in. It is also a very good idea to apply the Frontline every 28 days. More frequently than this is not recommended and probably of little extra benefit. Leaving it longer than 28 days is acceptable if fleas are not evident, but will not provide maximum control in the face of an outbreak.