Food allergy
Food allergy is an adverse immune response to a food, most importantly IgE-mediated reactions causing urticaria, angioedema, and anaphylaxis within minutes to two hours of ingestion. Diagnosis pairs a convincing history with skin or specific IgE testing and, when needed, a supervised oral food challenge, and management is strict allergen avoidance with epinephrine for reactions plus emerging oral immunotherapy.
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What this article covers
- Overview
Definition: food allergy is an adverse immune response to a food protein, most importantly IgE-mediated reactions that can cause anaphylaxis.
- Epidemiology
Common, especially in children: many childhood allergies (milk, egg, wheat, soy) are outgrown, whereas peanut, tree nut, and shellfish allergy often persist.
- Risk factors
Atopy: personal or family history of atopic dermatitis, asthma, or allergic rhinitis.
- Pathophysiology
IgE-mediated (immediate): food-specific IgE on mast cells triggers degranulation on ingestion, causing rapid urticaria, angioedema, and anaphylaxis.
- Clinical features
Immediate IgE reactions: urticaria, angioedema, oral itch, vomiting, wheeze, and hypotension within minutes to 2 hours.
- Differential diagnosis
Food intolerance (non-immune): for example lactose intolerance, causing gas and diarrhea without urticaria or anaphylaxis.
- Diagnosis
Establish with a compatible history plus IgE testing, confirmed by oral food challenge when needed: the diagnostic basis is a convincing clinical history of an immediate reaction to a specific food…
- Management
First, treat reactions as anaphylaxis: epinephrine 0.3 to 0.5 mg IM into the anterolateral thigh, repeated every 5 to 15 minutes, with airway support and IV fluids; give a second-generation…
- Complications
Fatal anaphylaxis: particularly with peanut and tree nut allergy and coexisting asthma.
- Prognosis
Variable by food: milk, egg, wheat, and soy allergies are often outgrown, whereas peanut, tree nut, fish, and shellfish allergies commonly persist.
- Prevention
Early introduction of allergenic foods: introduce peanut and egg in infancy (around 4 to 6 months), especially in high-risk infants, to reduce allergy.
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Related articles
- Anaphylaxis
Anaphylaxis is an acute, potentially fatal systemic hypersensitivity reaction from massive mast cell and basophil mediator release, presenting within minutes as skin, respiratory, cardiovascular, and gastrointestinal involvement after allergen exposure. It is a clinical, treat-first diagnosis, and intramuscular epinephrine is the immediate life-saving therapy.
- Urticaria
Urticaria is transient, pruritic, edematous wheals from mast cell histamine release, classified by duration into acute (under 6 weeks) and chronic (6 weeks or longer, usually spontaneous/idiopathic). Diagnosis is clinical with minimal testing, and treatment is stepwise second-generation H1 antihistamines up-titrated as needed, adding omalizumab for refractory chronic disease.
- Angioedema
Angioedema is self-limited, non-pitting swelling of the deep dermis and submucosa that follows one of two mechanisms: mast cell (histamine) mediated, which occurs with urticaria and responds to epinephrine and antihistamines, or bradykinin mediated, which occurs without urticaria and does not. Distinguishing the two determines whether treatment is allergic therapy or bradykinin-targeted therapy, and airway involvement is the central danger.