they shouldnt be allowed to make these things if they don't do what they say on the box!
I sent OH to Jolleys looking for Frontline and he rang me to say it wasn't there they only had a johnsons and bob martin one - I said might as well put whipped cream on them and expect it to ward off fleas.
OH, normally a quiet person said he complained loudly that they were all crap ones and the woman behind the counter gave him a funny look