IgE-mediated food allergy, a type I hypersensitivity reaction, occurs in 0.1% to 7.0% of the population. Almost any food can cause al-lergic symptoms. Any food can contain an allergen that results in anaphylaxis. The most common offenders are seafood (lobster, shrimp, crab, clams, fish), legumes (peanuts, tree nuts, peas, beans, licorice), seeds (sesame, cottonseed, caraway, mustard, flaxseed, and sunflower seeds), nuts, berries, egg white, buckwheat, milk, and chocolate (Parslow et al., 2001). Peanut and tree nut (ie, cashew, walnut) allergies are responsible for most severe food allergy reac-tions (Sicherer, Munoz-Furlong, Burks et al., 1999).
One of the dangers of food allergens is that they may be hid-den in other foods and not apparent to those susceptible to the allergen. For example, peanuts and peanut butter are often used in salad dressings and Asian, African, and Mexican cooking and may result in severe allergic reactions, including anaphy-laxis. Previous contamination of equipment with allergens (ie, peanuts) during preparation of another food product (ie, choco-late cake) is enough to produce anaphylaxis in those with severe allergy.
Clinical symptoms are classic allergic symptoms (urticaria, atopic dermatitis, wheezing, cough, laryngeal edema, angioedema) and gastrointestinal symptoms (itching; swelling of lips, tongue, and palate; abdominal pain; nausea; cramps; vomiting; and diarrhea).
A careful diagnostic workup is required in any patient with a sus-pected food hypersensitivity. Included are a detailed allergy history, a physical examination, and pertinent diagnostic tests. When test-ing for allergy, skin testing is used to identify the source of symp-toms and is useful in identifying specific foods as causative agents.
Therapy for food hypersensitivity includes elimination of the food responsible for the hypersensitivity (Chart 53-6). Pharma-cologic therapy is necessary in patients who cannot avoid expo-sure to offending foods or patients with multiple food sensitivities not responsive to elimination measures. Medication therapy in-volves the use of H1- and H2-blockers, antihistamines, adrenergic agents, corticosteroids, and cromolyn sodium.
Many food allergies disappear with time, particularly in chil-dren. About one third of proven allergies disappear in 1 to 2 years if the patient carefully avoids the offending food.
In addition to participating in management of the allergic reac-tion, the nurse focuses on preventing future exposure of the pa-tient to the food allergen. If a severe allergic or anaphylactic reaction to food allergens has occurred, the nurse must instruct the patient and family about strategies to prevent its recurrence. The patient is instructed about the importance of carefully as-sessing food prepared by others for obvious as well as hidden sources of food allergens and of avoiding locations and facilities where those allergens are likely to be present. The patient and family must be knowledgeable about early signs and symptoms of allergic reactions and must be proficient in emergency admin-istration of epinephrine if a reaction occurs. The nurse also ad-vises the patient to wear a medical alert bracelet or to carry identification and emergency equipment at all times.