I have mild allergies but when I was a kid they were pretty bad. I started taking allergy shots at age 4, and continued for 14 years. They helped but it was not dramatic and I have heard stories about people who outgrow allergies with no treatment at all.
So if I am exposed to pollen all the time, why doesn’t the exposure to pollen create immunity? What do the shots do that environmental exposure doesn’t do?
Well, for starters, they get into your blood, which pollen does not. The B cells patrolling your mucous membranes, like your nose, don’t provide very long-lasting immune memory. The ones in your blood last much longer. There’s more to it, I’m sure, but that’s one reason.
I’ve been getting shots on and off for almost 50 years. It certainly feels like it works. But I’ve wondered the same thing.
I used to have a strong cat allergy, but we adopted several and started a sort of cat rescue and the allergy vanished. I always figured the exposure burned the allergy out.
IIRC I read somewhere that there was medical debate about whether allergy shots did anything at all, but don’t remember a cite.