Our cats have always had Revolution as flea preventative. We (I guess) are bad parents, and only get it during flea season (and sometimes, not at all depending on where we're living). Our cats are fed raw, and sometimes get brewers yeast in their food to help combat fleas.
We really dislike using any chemical products if we don't have to, obviously.
We recently moved into a 3 apt building, basement level. The upstairs neighbours have dogs, so we got Revolution earlier this month to give the cats until flea season is done.
It's not been about a week since we applied, and our eldest cat (Zaq) has a bald patch where we put the meds!

It's got little raised red bumps, as well. He is not seemingly bothered by it, as I can fuss him and he just keeps doing cat things.
This is the FIRST time we've dealt with this issue! He's been on Revolution before, all the cats got a dose from the same box. No one else is losing hair or getting red bumps.
Anyone any ideas? I plan on ringing the vet tomorrow to ask, but as he doesn't seem bothered, I don't see the point in rushing him to the ER vet.