My husband is also extremely allergic to cats. When we first moved in together, I had to give up my beloved Pantani: http://flickr.com/photos/popps.....otostream/ (we have her shaved in the summer, and this is when it is growing out).
After a couple of years, I couldn't take it anymore. Pantani had been with me for about 5 years pre-hubby; she was my baby. My mom took her for three years when I went to law school, but I missed her so much.
So he agreed to give it a shot. We kept her out of the bedroom and off of the furniture he sat on. He didn't pet her at all for awhile. Then, little by little, he started to pet her. At first, he would always wash his hands immediately afterward. Long story short, she now sleeps with us and he doesn't wash his hands. If he pets her and touches his face, he still sneezes, but it's much better. (This was gradual. She's been back with us for 3 years now).
Funny thing is, he is still super allergic to others' cats. When we go to friends' homes who have cats, his allergies go crazy after a short time, even if he is sitting on a hardwood chair.
I had heard other people say that they built a tolerance to cats, but I didn't think it would happen with my guy because he is super allergic. He can't be in a cat person's home for more than about 15 minutes without going crazy. But, there you have it. Now, I have both. She just turned 12 in February. Love her.