This article is from the Miscellaneous Cat Information FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
In general, keep the cats out of the bedroom. If cats can be trained to keep off the furniture, that also helps. Substances like Allerpet C can be used on cat's fur to dissolve some of the dander and protein from the saliva that people are allergic to. Long haired cats have more area to deposit their saliva on and they have to be brushed (putting more dander in the air), so short haired cats are better for people with allergies. Clean and vacuum often; groom and brush the cat (outside if possible) often so its hair-shedding around the house is minimized; and bathe the cat regularly.
Some people are simply allergic to new cats. This kind of allergy means that it will diminish with repeated exposure. Thus you will not be allergic to cats that you are exposed to regularly; and actually become allergic to your own cat if you're away from it for some time. Washing hands frequently helps with this type of allergy.
Other people are allergic to the saliva on the cat's fur. A remedy for this is to bathe the cat once a month. No soap is needed, merely soak the cat thoroughly. Done on a monthly basis, it seems to keep the saliva levels down to a tolerable level. This was reported in a scientific journal somewhere; Cat Fancy covered it a few years ago. [exact reference?]
You may be allergic to cat hair, in which case you may want to get one of the breeds of cats with short, little, or no hair. There is a hairless cat, the Sphynx, and there are breeds of cat which are entirely lacking in the kind of hair (cats have four kinds of hair) most people are allergic to. These are the Cornish Rex or Devon Rex breeds, and their fur is short and curly.
You could go to an allergy specialist and get shots to help you with specific allergies. This can be expensive, but worth it, especially if you have other allergies as well. They'll test you for the things you're allergic to, and then give you periodic shots to help you develop an appropriate immunity to them. Be sure to find a specialist familiar with cat allergies: many will simply recommend you get rid of pets. Also, don't expect miracles. They can do a lot for you to reduce your allergies, but sometimes they can't track down a particular one, and sometimes it takes more than "just shots" to deal with an allergy.
The magazine New Woman (October 1992) has an interesting article about a cat-allergy vaccine. Catvax is being developed by the Immulogic Pharmaceutical Corporation (I.P.C.) in Cambridge, Massachusetts, and is now being tested on humans at Johns Hopkins University. Tests on animals indicate that Catvax is different from traditional cat-allergy shots in two ways. First, unlike conventional allergy therapy, which involves biweekly or weekly injections for up to a year, the vaccine may be able to completely prevent allergic reactions after just a few injections. Second, studies suggest that the vaccine will not produce allergic side effects, such as asthma, that traditional shots often do. I.P.C. hopes to complete its human studies and have the vaccine on the market by 1996 or 1997.
There is an informative article "When Humans Have Allergies: Ways to Tolerate Cat Allergies," in Cats Magazine, April 1992. The August 1992 issue of Cat Fancy contains an informative article; the September 1992 issue has a survey of people's experiences with allergies and what worked for them.