We use Revolution for our 4 cats, but the past few months I've noticed that one of them develops a small scab on the neck at the spot where I put it. I don't know if she scratches it or the Revolution causes the scab to form. It goes away after a few weeks, but I was wondering if anybody else noticed that? I looked up natural flea & tick solutions but I'm not comfortable with the ingredients they have in them. I don't like putting ANYTHING on the cats, but have to prevent the flea & ticks. Revolution works good but I was wondering about that scab.