Frontline Plus is a popular, fast and effective topically applied treatment and preventive for fleas and ticks. Frontline Spray is a less widely used form of the same medicine. Both Frontline products start killing mature fleas and their eggs on a dog’s coat within 24 hours. Doses are effective for one month, but the manufacturer recommends more frequent administration during tick season. Avoid bathing your dog immediately after applying Frontline in either spray or topical form.
Your Friend Frontline
Frontline products contains fipronil, the active ingredient that kills adult fleas infesting a dog. Fipronil works its way into the hair follicles, where it remains trapped by the sebaceous or oil glands, making it resistant to being washed away with bathing. The oil produced by the sebaceous glands also distributes the fipronil. Fleas need only to come into contact with the fipronil for it to be effective; they do not need to ingest it through a bite. Fipronil causes hyperstimulation in the fleas that come in contact with it -- it makes them appear more active than before application because it blocks the stabilizing ions in the fleas’ bodies. This hyperstimulation kills the fleas. Frontline Plus's second active ingredient, (S)-methoprene, is an insect growth regulator that kills flea eggs and larvae. This ingredient breaks the flea life cycle, preventing further infestation. Both fipronil and (S)-methoprene work for a month before Frontline Plus needs to be re-administered, tick season notwithstanding.
Frontline Plus is a waterfast preparation, but it takes a little time for the medication to become trapped in the coat’s sebaceous glands. Therefore, you should not give your dog a bath for 48 hours after applying Frontline Plus. The manufacturer, Merial, advises the same 48-hour interval for the spray form of Frontline. Use a soap-free shampoo to prevent the oils from being stripped from your dog’s coat, which would interfere with the product's distribution.
Before, Not After
If you know your dog will require a bath around the time his Frontline application is due and you cannot wait to bathe your dog for several days after application, bathe the dog before application. Use a soap-free shampoo to prevent natural oils from stripping from your dog’s coat, just as you would when bathing your dog after application. Apply the Frontline product once his coat is completely dry after his bath.
When Your Dog Gets Wet
Your dog might run through a puddle or get caught in the rain, or get wet in any number of incidental ways. Unless he gets utterly dripping drenched within 2 days of Frontline application, you won't have to worry about reapplying since it's waterfast. During the month between Frontline applications, your dog can do swimming or take a bath -- but the more he does, the less effective the Frontline may be toward the end of the month. During tick season, you'd be wise to apply every three weeks, particularly if the dog swims much.