We often hear clients complain that their dog still has fleas even though they treat monthly with a topical or oral product. It is assumed the products are not working. In reality, they likely are working, just as promised, but many people do not understand just how they work and their limitations.
Topical and oral products do not stop a dog from getting fleas. The fleas have to come in contact with the animal or the animal dander to suffer the effects from the pesticides. The products do not give an instant kill. It can take 12 hours to kill the fleas. In that 12 hours, they are able to bite causing an allergic reaction and reproduce.
The Advantage Multi insert explains:" Advantage Multi for Dogs should be administered at one-month intervals. If the dog is already infested with fleas when the first dose of Advantage Multi for Dogs is administered, adult fleas on the dog will be killed. However, reinfestation from the emergence of pre-existing pupae in the environment may continue to occur for six weeks or longer after treatment is initiated."
That is very important information. One thing it does not approach is that the above is a controlled scenario. If the environment is getting reinfested during that 6 weeks from other animals, like stray cats or dogs, the flea population is continually growing. Additional fleas are being dropped in the environment and reproducing. When those jump onto the pet, they too need up to 12 hours of contact to be killed by the products. With only topical and oral products being used, it is a never ending cycle of fleas for the pets.
The topical and oral flea products are meant to prevent infestations. If the environment is clear of flea infestation, the products will usually kill any fleas a pet might pick up on a walk or from the occasional stray that wanders onto the property. The kill is usually fast enough to prevent a huge population growth and infestation.
Unfortunately, many owners only use the products after they see fleas on the pet. At that time, the environment is usually infested or at least has a good number of flea eggs left around to hatch out.
If an infestation is present, if the dog is continually picking up fleas, it is important to find the source. They come from somewhere. They do not just magically appear on the dog. They must be killed there, at their source, in order for the dog to remain flea free. In most cases, that requires spraying the yard and the house. This is not a one time thing. The sprays do not kill the fleas in every part of their life cycle. Some will kill the adults and the larvae. Some will kill the eggs. None will kill the egg, larva, pupa, and adult stages. The treatment needs to be done every 10 - 14 days, for approximately 6 weeks to catch and kill the fleas at all stages.
Once the environment is clear, and steps are taken to avoid reinfestation from roaming animals, the once a month products can usually do a great job keeping an infestation from occurring again. The owner may still see the occasional flea on the pet. Remember, it can take up to 12 hours for them to die. For myself, if I see 2 or 3 fleas on a pet that is regularly treated, I consider the product doing it's job. If I see a dozen or more fleas on a pet that is regularly treated, the environment is in need of treatment.