Have you tried a solution called 'Petal Cleanse'? I anticipated problems with my OH when we got our cat, and started using this- his reaction to the cat has now gone! It's quite easy- groom the cat, put some of the solution on a cloth/flannel and wipe it over the cats coat, then wipe with a dry flannel to remove the excess! I think its about £10 a bottle, but we've had ours 3 months now and there's still plenty left.
BTW it says its completely safe for cats, even if they lick it off. You can also buy sprays for furniture etc which I used when a friend with a cat allergy visited- he seemed OK too.

HTH

Claire