We have two cats and two dogs, all of which are severely infested with fleas. I have used dips, sprays, and flea collars, and have treated the yard as well. We still have fleas, and they are driving our animals crazy. What should we do?

It takes a lot of work.

Fleas continue to be an important problem of animal husbandry despite the advances in flea-control products. Using conventional insecticides, one must address fleas on the pet, in the house, and in the environment, a three-pronged approach. Dips are not safe when used often enough to be effective. Flea collars are not generally useful, and sprays must be applied regularly to have maximum kill. The yard products, such as organophosphates, should help eliminate environmental fleas. You may wish to treat the shady areas of the yard, under bushes and trees, where ultraviolet light does not penetrate, especially if the pets lie there. You did not indicate whether the animals enter the house or garage, or if they go in the car, but all areas that your pets visit must be treated, especially with growth hormone regulators. The entire environment and the pets must be treated concurrently; the clean, flea-free animals must be housed in a flea-free area while the premises are treated. After vacuuming the area rugs, be sure to throw the vacuum bag away. Despite the apparent expense of the new, topical products such as Frontline or Advantage, these products have proved themselves highly effective in such situations. They should be safe for all members of the household. Please discuss their utility with your veterinarian. He or she will assess your situation and customize a flea-control plan for you as economically as possible. For more information about fleas, please refer to the VetCentric Encyclopedia article titled, "Flea Control, Canine and Feline."