Due to the flea lifecycle, and the ability of pupae to lay dormant, ongoing treatment for your pets is really important.
Despite your best efforts it is impossible to definitely kill or remove all flea pupae. This means that there may be dormant pupae in the house. Although we are not sure exactly how long these pupae can lay dormant for, it may be as many as 21 months. At any point a dormant pupa could hatch, and will look to your pet as a food source.
If you have continued with comprehensive flea protection for your cats and dogs, this newly hatched adult flea will die before laying any more eggs. Slowly, all dormant pupa will hatch, die or be removed, and your treated pets will prevent another infestation from developing.
Your treated pets will also kill any new fleas that have been brought into the house, making sure that a new population cannot establish itself.