If you are not familiar with desensitization shots, then it sounds like you
have not been to an allergist.  Please ask your girlfriend to make an
appointment with one before you make this decision.  Your GP may not be the
best source of advice on allergies.  There are other people on this
newsgroup with severe allergies who have used allergists, so maybe one of
them will respond with more information.  Also, my brother-in-law had severe
allergies, and he was greatly helped when we installed an electrostatic
filter on our heat pump.  This was a permanent electronic filter installed
in the equipment, not one of those temporary disposable filters.

MaryL

I am sorry about your girlfriend"s allergies.  An allergist  can,
through tests, determine a specific allergy (or allergies) and create
a shot to be given at regular intervals to build up resistance to that
particular thing.  It may take a while, but can be very successful
Allergies are usually hereditary.  I and my family all have allergies.
By the time I was 19 I had to discontinue perfumes  and makeup.  I was
allergic to my bosses aftershave  etc.
Another thing, if you brush and comb your cats daily, use an
electronic filter in the house , it really can help.  When my son was
about five, I had to eliminate the rug in his bedroom  and put covers
on the mattress , get rid of feather pillows, etc.  (There are lots of
books on allergies).  I even had a mohair chair. I had to get rid of.
Well, enough of this -- it could go on forever.  I personally feel
that allergies today are aggravated by air pollution, which only seems
to get worse.   Best of luck in our endeavors.   MLB