Food Allergy

Key Features

• Most common IgE-associated food allergens in children are milk egg, peanut, soy, wheat, tree nuts, fish, and shellfish

• In older patients, fish, shellfish, peanut, and tree nuts are most often involved in allergic reactions, and may be lifelong allergies

• The highest prevalence of food allergy is found in children with moderate to severe atopic dermatitis, with approximately 35% affected, whereas chronic conditions such as urticaria and asthma are much less likely due solely to food allergy.

• Causes of food allergy

  • IgE-mediated

    • Gastrointestinal: Pollen-food allergy syndrome, immediate gastrointestinal anaphylaxis

    • Cutaneous: Urticaria, angioedema, morbilliform rashes, and flushing

    • Respiratory: Acute rhinoconjunctivitis, acute wheezing

    • Generalized: Anaphylactic shock

  • Mixed IgE- and non–IgE-mediated

    • Gastrointestinal: Eosinophilic esophagitis/gastroenteritis/colitis

    • Cutaneous: Atopic dermatitis

    • Respiratory: Asthma

  • Non–IgE-mediated

    • Gastrointestinal: Food protein–induced enterocolitis, proctocolitis, and enteropathy syndromes; celiac disease

    • Cutaneous: Contact dermatitis, dermatitis herpetiformis

    • Respiratory: Food-induced pulmonary hemosiderosis (Heiner syndrome)

Clinical Findings

• For all IgE-mediated reactions, reactions to foods occur within minutes and up to 2 hours after ingestion

• For non–IgE-mediated and mixed disorders, reactions can be delayed in onset for more than several hours, such as in FPIES, to possibly days later with onset of vomiting or an eczema flare after food exposure due to eosinophilic esophagitis or atopic dermatitis, respectively

• At times, acute symptoms may occur, but the cause may not be obvious because of hidden food allergens

• Hives, flushing, facial angioedema, and mouth or throat itching are common

• In severe cases, angioedema of the tongue, uvula, pharynx, or upper airway can occur

• Gastrointestinal symptoms include abdominal discomfort or pain, nausea, vomiting, and diarrhea

• Children with food allergy may occasionally have isolated rhinoconjunctivitis or wheezing

• Rarely, anaphylaxis to food may involve only cardiovascular collapse.

Diagnosis

• A thorough medical history is crucial in identifying symptoms associated with potential food allergy

• History of a temporal relationship between the ingestion of a suspected food and onset of a reaction—as well as the nature and duration of symptoms observed—is important in establishing the diagnosis

• Prick skin testing is useful to rule out a suspected food allergen

• Double-blind, placebo-controlled food challenge is considered the gold standard for diagnosing food allergy, except in severe reactions

Treatment

• Elimination and avoidance of foods that have been documented to cause allergic reactions

• Consultation with a dietitian familiar with food allergy may be helpful, especially when common foods such as milk, egg, peanut, soy, or wheat are involved

• All patients with a history of IgE-mediated food allergy should carry self-injectable epinephrine (Auvi-Q or Epipen) and a fast-acting antihistamine, have an anaphylaxis action plan, and consider wearing medical identification jewelry