Frontline normal absolutely not enough in strong flea infestation.
The combing with a flea comb makes visible what I had suspected. Despite treatment (2 times at intervals of 4 weeks) is crawling on our cat only as of fleas.
Fleas lay their eggs while on the cat, but they fall very quickly, and then spread throughout the surrounding area.
Have they first spread in the surroundings of the cat, it is very hard to get the flea plague under control. Also constant vacuuming then brings not much (Tip: Because the fleas can escape from the vacuum cleaner, you should replace the bag after each vacuuming However, this is very expensive A piece of a flea collar in the bag ensures that the fleas in the bag.. are killed).
I'm going to definitely switch to Frontline Combo, and Frontline can be normal if at all then most recommend for flea prevention, the effect is otherwise simply too weak.
Addendum: With Frontline Combo we now get our really heavy flea plague under control (in severe infestation needs to be patient, but after the second application, we were going on the fleas).
