Sorry for the delay in replying. I have been having a very stressful time with Samson.
Thank you for the link that you gave me.
I switched him to a product containing imidacloprid as you suggested.
The odd “flea newcomers” that I previously mentioned, turned out to be infestations deep in his fur, on his skin.
Impossible to comb out and driving him spinning madly, salivating and grooming himself excessively, again he is wet all over.
I searched the web for information on “cat flea infestation”.
It seems that this same problem is very common this year and Frontline seems ineffective in controlling it.
Other people have also changed to Advantage.
In desperation I managed to arrange a visit to my Vet.
She has seen this problem many times recently.
She gave him immediately one Capstar tablet to kill off the livestock and a Colvasone injection to relieve the irritation.
We will then start him on a course of Activyl spot on.
She also suggested that come Springtime it would be beneficial to start him on Program injections.
At last he seems to be having a calm day today.