Frontline and Frontline Plus are two types of drugs from the same company i.e., Merial. Both are used mostly to completely remove or reduce the population of tick or flea around a pet. However, there are some differences between the two. One of the main differences between the two is their year of production.
Frontline was released in 1997, and that makes it the older of the two, whereas Frontline plus was first released in 2000. Although both are very effective, the frontline is not as effective as Frontline Plus. Another difference is that Frontline cannot be used to kill both young and adult flea and tick, whereas Frontline plus kills both.
Also, Frontline plus seems to be ideal for outdoor pets, while Frontline works perfectly for indoor pets. Aside from these little differences, both contain the same active ingredient, which is Fipronil. Both are usually applied on the skin, and that makes Fipronil to be easily absorbed into the body of the animal.