Food allergies are adverse immune reactions to food proteins, classified as IgE-mediated, non-IgE-mediated, or mixed. IgE-mediated (type I hypersensitivity) reactions occur within minutes to 2 hours of exposure and involve mast cell degranulation triggered by allergen-specific IgE binding. Symptoms range from oral allergy syndrome and urticaria to angioedema, respiratory distress, and anaphylactic shock. Common allergenic foods include peanuts, tree nuts, milk, eggs, soy, wheat, fish, crustacean shellfish, and sesame (the “Big 9” in many jurisdictions). The prevalence of food allergy in children is approximately 5-8% and in adults 3-5%.
Non-IgE-mediated food allergies involve cell-mediated immune responses. Celiac disease is an autoimmune enteropathy triggered by gluten (prolamins in wheat, barley, rye) in genetically susceptible individuals (HLA-DQ2/DQ8), causing villous atrophy, malabsorption, and elevated tissue transglutaminase antibodies. Food protein-induced enterocolitis syndrome (FPIES) presents with delayed, severe vomiting and diarrhea, typically triggered by milk, soy, or grains in infants. Eosinophilic esophagitis is a mixed IgE/non-IgE condition with esophageal dysfunction and eosinophilic infiltration.
Food intolerances are non-immune adverse reactions. Lactose intolerance results from lactase deficiency, causing bloating, diarrhea, and gas after dairy consumption. FODMAP intolerance involves fermentation of fermentable oligo-, di-, monosaccharides and polyols by gut bacteria, triggering IBS-like symptoms. Sulfite sensitivity (asthma-like reactions) affects sulfite-sensitive asthmatics and is managed by avoiding sulfited foods. Diagnosis of intolerances relies on clinical history, elimination diets, and challenge testing, rather than allergy testing.
Diagnosis of IgE-mediated allergy involves skin prick testing (SPT) with allergen extracts, specific IgE measurement (ImmunoCAP), and the oral food challenge (OFC), which remains the gold standard. Management relies on strict allergen avoidance, emergency action plans, and adrenaline auto-injectors for anaphylaxis. Food labeling regulations (EU FIC, US FALCPA) require declaration of major allergens in ingredient lists. Precautionary allergen labeling (“may contain”) is not regulated and can lead to risk-taking behavior or unnecessary restriction. Allergen management in food production is critical for protecting allergic consumers. Unlike biogenic amine reactions, food allergies involve the immune system. HACCP plans must address allergen cross-contact.
