Inexperienced application of over-the-counter pest control products are generally ineffective and can also be unsafe for pets, children, and adults if used improperly. Also, most pests return unless you take steps to prevent them. Without proper care in as little as few weeks, new infestations can develop.
The only effective way to eliminate and prevent new infestations is to use a reputable pest prevention company with an ongoing service plan, such as Stop Bugging Me! Pest Control.