My husband and I are not allergic to cats, but we have good friends who are. Before our allergic friends come to visit, we vacuum the house thoroughly (includes furniture) and this seems to make a huge difference. Also, Miss Bo isn't one to climb on people's laps and get into their faces, so that probably helps as well.
One more thing.....we purchased a Rainbow vacuum cleaner last year, and although it's terribly expensive, it's the best cleaner we've ever had. Instead of using a bag, which clogs up quickly and reduces the suction power, the Rainbow uses a bowl of water to filter the air as it vacuums. Talk about efficient!! Our house is a lot cleaner now since we got the Rainbow, and I have allergic friends who use it and swear by it.