I am looking for the most user-friendly (for cats and people) flea treatment. The choices include--but are not limited to--Frontline, Activyl and Revolution. What has your experience been? Side effects? How long will the treatments have to continue? I used Frontline once at the beginning of August. Our cat, Fenny, seemed sluggish for a few days after treatment, but the fleas and their biting have stopped. Frontline is rumoured to be less effective due to having been used for a number of years. Our vet has suggested Activyl and Revolution. Your help would be appreciated. I am concerned about the toxicity of these products to pets and people.