When it comes to allergy shots, many folks are not aware that there are TWO very different allergy shot protocols available in the United States.
The largest allergy shot system available is by the American Academy of Allergy Asthma and Immunology (AAAAI). The physicians who use this protocol come by way of internal medicine training.
The other allergy shot system (which is the protocol we use in our office) is available by way of the American Academy of Otolaryngic Allergy (AAOA). The physicians who use this protocol (like myself) come by way of Otolaryngology-Head & Neck Surgery (aka, ENT or Ear Nose Throat) training.
Each system uses a different method of how the allergy vials are made. Also, the buildup protocol is different. Just as in baking... there are many ways to bake a cake.
Physicians of one or the other system often pooh-pooh the other, but both systems are based on evidence and are effective.
Where I work in Warrenton, Virginia, our practice (using AAOA) and another (using AAAAI) are the only two practices that provide the full suite of allergy testing and allergy shots. Given both our practices use a different system, I've seen firsthand the benefits of having two different systems available when it comes to allergy shots.
For whatever reason (and this is a personal observation of mine that I can't prove), not all patients respond to allergy shots with one system, but DO respond using the other system. It's not that one system is better than the other... it's just different... and patients benefit from that.
The analogous scenario which I also see involve allergy medications... for some folks, allegra works best whereas for another, allegra does not work at all, but zyrtec works great.
The basic rule of thumb when it comes to allergy shots is that a patient should experience SOME improvement in their allergies after being on shots for at least 1 year. 80% of patients do... For the other 20%, it may be worthwhile to stop and try the other allergy shot system.