With my daughter, the vomiting in this case would have definitely been the adrenal reaction due to the allergic reaction.  Happens to her more than we care to admit. She is allergic to eggs...and has always had an adrenal crisis situation when she accidentally ingests them. You wouldn’t believe the things they hide eggs in...candy, ice cream, bread, rolls, etc! We check all labels and still goof up once in awhile! Makes eating out in restaurants or at friends’ homes a challenge, not to mention camp. But at 11 now, she does her own label-checking and is extremely responsible about it. 

p.s. they didn’t believe me either at first about the adrenal crisis caused by an allergic reaction.  Hang in there!