This poll is the only place I've noticed you mention it, and I originally read the poll as helping you make up your own mind in isolation from others. I didn't think about whether you'd ask them or not, and I think that's where my original comment came from.

Thinking about it more now, even suggesting getting a cat when someone in the house is known to be allergic seems like a rude and ill-considered thing to do. I mean, what would happen if the allergic housemate said yes, and then it turned out s/he couldn't take it? And how horrible would the housemate feel if you were all puppy-dog-eyed going "please please, just one little kitty" and the housemate were all "I hate cats, plz die now, 'kay"? I just don't think it's a fair position to put the housemate in since you already know s/he's allergic.

FWIW I'm allergic to everything with fur, so I'm bound to be more sympathetic to the allergic housemate.