Frontline Plus is a drop-type topical flea treatment applied monthly between your dog’s shoulder blades. The active ingredients in Frontline Plus work together to control the fleas on your dog and in your home. The first of these, fipronil, kills any adult fleas that hop on your dog for the entire month. The second ingredient, (S)-methoprene, breaks the flea life cycle by killing existing eggs, preventing fleas from laying fertile eggs and by stopping flea larvae and pupae from developing.
The ingredients in Frontline Plus have a good safety record; the treatment is safe enough to use on puppies as young as 8 weeks of age as well as on pregnant dogs, as long as dosage is correct -- smaller dogs get smaller doses. Unless your dog is highly sensitive to the ingredients in Frontline Plus, the worst that’s likely to happen to him if he licks it while it’s fresh is that he’s going to drool a lot because it doesn’t taste too good. Don’t use it if you know that your dog is allergic or reacts poorly to alcohol or insecticides.