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Scott you're talking to someone who had Immunotherapy for like 5 years and got allergy shots. It helps A LOT, but it doesn't make you completely immune to allergies. They give you progressively larger doses of allergens to make your system adapt to it, but you will never be completely immune (doctor's words not mine). Basically if I go say and mow the lawn I still get a reaction, but not as bad as it used to be. I can also go around outside without having to take any Allegra or anything. I used to have to take it daily, hence why I got shots. The thought of taking a pill every day for the rest of the day was just bleh.
Also maybe you should read the articles too

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Finally, some allergy sufferers find relief in periodic injection therapy designed to stimulate the body's natural immune responses to the cat allergen. Although this is not usually 100% successful, it can reduce reactions to tolerable levels for many individuals
That's me so I agree with you there. However:
Many people originally allergic to cats have, over time, become "immune" to allergic symptoms from their own cats; however, they may still have allergic reactions, of varying intensity, to other cats. This is not reliable when deciding to get a cat as a pet, as allergy may become worse, not better, with time.
Again, I don't doubt shots lessen allergic reactions since I'm living proof, but completely immune is not going to happen. Folks like me who got shots which were inconvenient for a few years did it so it'd be better later on in life and it is. I'm not doubting that claim. I'm doubting this complete immunity claim because I've done the therapy you're referring to and I'm not completely immune to anything I was previous allergic to. If I have a high dose of an allergen, my body will still react. It's in my DNA (my father has nearly the same allergies). Like it'd be dumb for me to put my face in a cat and rub it around.
In all honesty, and I'm completely speculating, I think folks who say they're now completely immune to their cats might be doing something psychologically they're not aware of. The mind is a pretty good placebo and I wouldn't be surprised if folks like their cats so much or live with them so long that they learn to cope with the reactions or their mind convinces their body that they're OK. It's not an unheard of thing.
However, I for one, even after 5+ years of shots, still get reactions around cats, pollens, grasses, etc. so it goes without saying I'll never own a cat

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Awesome...Sunny the fat dog.
Edit: I also just re-read your post and you said tolerance not immunity (the wikipedia article however said that immunity claim). I 100% agree with you on the tolerance claim. The shots have done wonders for me and I almost never have to take medication now. I used to take one every day or just going outside would be unbearable (I'm allergic to literally EVERY tree, grass, pollen in America -____________________-). Anyway looks like we agree on tolerance so my post was probably unnecessary. BLEH.