Food Allergy

Food allergy is an adverse immune response that occurs reproducibly upon exposure to specific dietary antigens, most commonly proteins found in certain foods. The pathogenesis primarily involves an aberrant immunoglobulin E (IgE)-mediated hypersensitivity reaction, although non-IgE-mediated mechanisms can also contribute. In sensitized individuals, ingestion of the offending food triggers immune cells such as mast cells and basophils to release mediators like histamine, leading to a spectrum of clinical manifestations ranging from mild urticaria and gastrointestinal symptoms to life-threatening anaphylaxis. The health impacts of food allergy are substantial, encompassing acute morbidity, risk of fatal reactions, psychosocial stress, and significant dietary restrictions that can impair nutritional status and quality of life. Food allergy also imposes a considerable burden on healthcare systems and affected families due to the need for ongoing vigilance, emergency preparedness, and medical care.

Ige-Mediated Food Allergy

This type is characterized by an immediate hypersensitivity reaction that occurs within minutes to two hours of exposure to the allergenic food. The immune system produces specific IgE antibodies against food proteins, which bind to high-affinity receptors on mast cells and basophils. Upon re-exposure, these antibodies cross-link with the allergen, triggering cellular degranulation and release of histamine and other mediators. Clinical manifestations include urticaria, angioedema, respiratory distress, gastrointestinal symptoms, and, in severe cases, anaphylaxis.

Non-Ige-Mediated Food Allergy

In this type, the immune response does not involve IgE antibodies but rather other components of the immune system such as T cells. The onset of symptoms is typically delayed, occurring several hours after ingestion. Non-IgE-mediated food allergies often present with chronic gastrointestinal symptoms, including vomiting, diarrhea, and failure to thrive, and are commonly implicated in conditions such as food protein-induced enterocolitis syndrome (FPIES), allergic proctocolitis, and eosinophilic gastrointestinal disorders.

Mixed Ige And Non-Ige-Mediated Food Allergy

Some food allergic disorders, such as atopic dermatitis and eosinophilic esophagitis, involve both IgE-mediated and non-IgE-mediated immune mechanisms. These mixed reactions can present with both immediate and delayed symptoms affecting the skin and gastrointestinal tract. The pathophysiology is complex, involving both antibody- and cell-mediated responses to food antigens.

Epidemiology

Food allergy affects approximately 6–8% of children and up to 3–4% of adults worldwide, with prevalence rates varying by age, geography, and diagnostic criteria. The incidence has increased in recent decades, particularly in industrialized countries. The most common food allergens include cow's milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish, with peanut and tree nut allergies being more persistent and associated with severe reactions. Prevalence is highest in early childhood, with some children outgrowing allergies to milk, egg, wheat, and soy, while allergies to peanuts, tree nuts, fish, and shellfish tend to persist into adulthood. Food-induced anaphylaxis is a leading cause of anaphylactic reactions in children and young adults, and food allergy is associated with increased healthcare utilization, emergency department visits, and risk of accidental exposures.

Diagnosis

The diagnosis of food allergy involves a comprehensive clinical assessment beginning with a detailed history of reactions, including the suspected food, timing, symptoms, and reproducibility. Physical examination may reveal signs of atopy such as eczema or allergic rhinitis. Diagnostic testing includes skin prick testing and measurement of serum food-specific IgE levels, which are sensitive but not specific and must be interpreted in the context of clinical history. Elimination diets followed by oral food challenges under medical supervision remain the gold standard for confirming diagnosis, particularly in cases of inconclusive test results or non-IgE-mediated allergies. For non-IgE-mediated reactions, diagnosis relies heavily on clinical history and resolution of symptoms upon elimination of the suspected food, as laboratory tests are generally unhelpful. Component-resolved diagnostics and basophil activation tests are emerging tools that may improve diagnostic accuracy in selected cases. Differential diagnosis includes food intolerance, celiac disease, and other causes of adverse food reactions.

Launched Drugs

Peanut (Arachis hypogaea) allergen powder-dnfp is an oral immunotherapy product indicated for the mitigation of allergic reactions, including anaphylaxis, that may occur with accidental exposure to peanuts; it is administered in a controlled, escalating dosing protocol to induce desensitization in individuals with confirmed peanut allergy. Omalizumab is a monoclonal antibody that binds to IgE and prevents its interaction with high-affinity IgE receptors on mast cells and basophils, thereby reducing the risk and severity of allergic reactions in patients with food allergies; it is used as an adjunctive therapy in selected cases to improve the safety and efficacy of oral immunotherapy or to reduce allergic symptoms.