Hi Kirsten... you are right to be concerned about this reaction. My dd is 5 and has severe food allergies - dairy, peanut and soy, with anaphalactic reactions. We have been through a lot with this situation and I would be happy to pass on what I have learned in hopes that it can be of help.
She started having reactions at 1 week (severe excema) and it took over two years to figure out the food allergies. (She was reacting to my diet through breastmilk.) We went through the whole spectrum of specialists, from conventional medicine to alternatives. I could write a book on it at this point, so I won't try to tell it all in this post, but I have learned a lot and would be happy to pass on anything that might help. I just don't know where to start!
It's true that reactions can get worse each time. I think you should not hesitate to take her to an allergist. I can't remember at what age they start skin testing, at one year they may just do a blood test. (Which of course is awful and traumatic but not the worst thing in the world) But I don't think you need a test to know she had a reaction. From what I know, any kind of facial swelling indicates a severe reaction, because swelling outside can mean swelling on the inside too (throat). I'm not trying to scare you, I just want to support you in taking this very seriously, as one who has been there.
One thing I have to tell you is that ALL, and I mean ALL! the important things I learned about food allergies have come not from the doctors but from knowledgeable moms who have educated themselves in order to help their children. In fact - this is off on a tangent but I just have to make the point - my dd was going to the "best" dermatologist in our area for 2 years for excema, and they NEVER suggested the possibility of food allergies. I finally made the connection thanks to an online bullitin board dealing with allergies. There are some wonderful online resources for food allergies that will save you thousands in Dr. bills. Start with www.foodallergy.org
Severe food allergies ARE a life changing condition (for the whole family, really) but better to know and be prepared than not.