Hi there....
My cat, Wobble, cannot tollerate any kind of collar around his nexk. We had him microchipped instead of the normal collar and tag, and also flea collars, I have ound, are not really that good. We used them in the sanctuary for a while and they irritated quite a few of the cats.
Front Line.....which you can get from the vets......is really good. Although its more expensive than the collars, it lasts up to 6 months so if you work it out, it does make it cheaper.
Its just a few drops of liquid which you place at the nape of the animals neck and really does work well.
Hope this has helped!