I don't think it's odd for her to have only one allergy, but seriously if he said he doesn't know what to test for you need to get her to another allergist! My daughter had her first skin test at around 3yrs. She never had any rash or swelling. She had begun throwing up a couple times a week and immediately after, she would be fine. I knew that was not normal and because my nephew has some serious food allergies I know it affects ppl in all different ways. So we had no idea what was causing the reaction and in her first test they probably tested for around 30 or more items. I have just had my 1yr old son tested a few weeks ago because he had a serious egg reaction and he is allergic to eggs and nuts. My daughter's first test showed Peanuts, strawberries, corn, and some outside stuff. Some of those have gone away now as she's almost 6. They need to definelty test your daughter for all dairy, nuts, outside allergins, and i would have them do corn because it's in everything! Think about how much daily we get that has corn starch or cornsyrup. I believe that was the culprit of my daughter's vomiting because she was getting so much of it. Good luck. I hope you find out something.
OMG Thats just what I have, except I am allergic to shrimp