> I would happily recommend the Frontline spray as safe, tried and tested. And I don't work for the manufacturers!
While I haven't found a single flea on my dogs for nearly 3 years (since the sad loss of my cat, who did tend to bring them in), my flea regime was/is Acclaim to treat the house with, at least once a year, whether you have seen fleas or not - it prevents them breeding - and for any occasional fleas seen, a quick squirt of Frontline spray.
There is no need to use the spot-ons, and every reason to question the ethics of putting chemicals on your dogs' skin on a monthly basis. The Frontline spray will work, because the fleas have not gained resistance to the deluge of spot-ons.
It also happens to be the most cost-effective form of flea preventative, a huge saving on the cost of individual monthly treatments for each animal in the home. You need to be registered with a vet to get the Frontline spray, which costs around £25-£30 (but will last a year or more and is safe on cats and dogs - also ferrets). Acclaim household spray can be bought from most branches of Boots and is circa £14 which is enough for 1-2 house treatments, per 6months/year. Compare that with the cost of spot-ons for each of your dogs (and cats if you have any) and you can see how simple it can be to keep on top of fleas.