A research paper by Wang & Sampson declare food allergy as very common. http://www.ncbi.nlm.nih.gov/pubmed/21364287
They say: “Food allergies affect up to 6% of young children and 3%-4% of adults. They encompass a range of disorders that may be IgE and/or non-IgE mediated, including anaphylaxis, pollen food syndrome, food-protein-induced enterocolitis syndrome, food-induced proctocolitis, eosinophilic gastroenteropathies, and atopic dermatitis (eczema). Many complex host factors and properties of foods are involved in the development of food allergy.”
Every one with on-going symptoms needs to be assessed for food allergy.