While looking at ways to make Grendel, Jaques, and Isis co-exist more comfortably in our house, Kris recommended some Feliway, which has a good record, in the CPL’s experience, of helping cats stay happy under changed circumstances; it replicates some key cat pheremones and makes the place smell (to a cat) like everything has been thoroughly marked safe.
Unfortunately, I’ve discovered it’s got one drawback: if, like me, you’ve got cat allergies, having Feliway gently disperses through the whole house automatically is not such a good thing. In fact, it turned out to leave me with a constant haze of asthma and migranes. I’ll probably try it again in case it turns out that it was something else causing the problem as a coincidence, but it looks like Feliway isn’t for everyone.