What is the difference between Frontline Original and Frontline Plus?
Frontline Original is the original spot-on formulation that Frontline first entered the market with in Australia. The single active ingredient is Fipronil which is a flea adulticide (ie it only kills adult fleas).
Frontline Plus was released a few years after Frontline Original and in addition to Fipronil, it also contains the active ingredient s-methoprene which is an insect growth regulator. What this means is that Frontline Plus can kill immature stages of the flea life cycle (ie eggs, larvae and pupae) in addition to the adult stages.
The immature stages of the flea lifecycle occur off the dog/cat, so the added benefits of the insect growth regulator would be greatest in instances where your pet frequently comes into contact with other untreated animals or environments, or where there is a significant pre-existing flea burden present. If your dog or cat leads a sheltered existence (ie. inside only cats, or dogs that rarely go visiting other dogs or environments) then Frontline Original is perfectly adequate when used according to the label directions.
Both products take 12-24 hours to kill adult fleas and both products require monthly application all year round to maintain effective flea control.
In addition, both products provide the same level of tick protection on dogs. Note neither product is registered for tick control on cats in Australia. For tick control on cats in Australia you will need to consider Frontline Spray.