It sounds odd that you had a reaction to a shot out of the same bottle you had used previously. I think I'd ask for a new bottle though, just in case there is something wrong with the serum.
I tried a couple of allergists until I found one I liked. My problem was food intolerances, in particular foods containing sulfites. This of course, is not treatable with shots, but the first two allergists didn't believe in it. I also have a few pollen allergies plus dust and mites, which the shots control very well.
My allergist got me started keeping a food journal, which identified my food intolerances. I also write down all my meds, drinks, and the time I take everything and also reactions and the times of those. I would suggest to everyone with any sort of allergies to keep a journal. It really helps with finding the real culprits responsible for reactions. There are many posts on this, which you can find using the search box at the top of the page.