E (ssIgE) tests because of their increased sensitivity, greater validity, and lower costs.2 Use of allergen-specific IgG testing, cytotoxicity assays, applied kinesiology, provocation neutralization, or hair analysis is not recommended because of insufficient evidence in the literature of their value. A positive skin-prick or ssIgE test should be followed by an OFC to establish a diagnosis. An OFC corroborates or excludes a suspected food allergy by having the patient eat small, but increasing, amounts of a suspect food. The OFC begins with the introduction of a suspicious food every three to five days. If the food eaten during the OFC elicits an allergic symptom, the diagnosis of food allergy is confirmed. If the patient eats the food without any symptoms produced, the diagnosis of food allergy is ruled out. If the patient’s history of food reaction is mild, the OFC can be conducted at home with proper education and an emergency treatment plan in place. Otherwise, the OFC is conducted in an allergy specialist’s office. An OFC is preceded by a one- to two-week elimination diet in which all suspected foods (i.e., those with positive skin-prick or ssIgE test results) are excluded from the diet. This process is used to identify foods that may be causing an adverse effect in patients. The goal of the elimination diet is to return the individual’s food allergy symptoms to baseline if possible. It is important that the patient symptoms normalize prior to starting the OFC to allow a means of objective measurement. If the patient’s symptoms do not return to baseline with the elimination diet, further evaluation is needed. It is uncommon for a person to be allergic to a food he or she has previously eaten successfully. Food allergies usually follow a predictable path, so if a patient has allergy-type symptoms to a previously tolerated food, consideration should be given to an alternative diagnosis. Differential diagnoses for food allergy include bacterial infection, eczema flare from nonfood exposure, eosinophilic esophagitis, food intolerance (a non-IgE-mediated reaction to food that can cause the same symptoms as a food allergy), gallbladder disease, gustatory rhinitis, Heiner syndrome, infection from contaminated foods, pancreatic insufficiency, parasitic infection, protein-induced proctocolitis/enterocolitis, and pyloric stenosis.4
TABLE 2. Key questions for patients What particular food do you suspect caused the reaction? How much of the suspected food did you eat? What other foods did you also eat at the time the reaction occurred? Do you know (or can you get a list of) all the ingredients in the food product? How was the food prepared and served? Did you have similar symptoms on other occasions when the food was eaten? What was the time lapse between eating the food and the reaction beginning? Do you have a history of avoiding or refusing to eat the suspected food?
(Table 3).7 The first-line treatment for anaphylaxis in all patients is epinephrine (Adrenaclick, Adrenalin, Epi-Pen, Twinject). A delay in the use of epinephrine will increase the risk of death. Onset of anaphylaxis may occur as quickly as several minutes postexposure or up to 72 hours later. In 20% of all anaphylactic reactions, patients may experience a biphasic anaphylactic reaction, with the second phase occurring shortly after the first without further exposure to the provoking allergen.8 Because a second dose of epinephrine is the preferred treatment in biphasic reactions health-care providers should prescribe epinephrine injectors in packs of two and instruct the patient to carry both doses at all times. Several types of epinephrine auto-injectors are available. Regardless of the type used, the dose is 0.3 mg for individuals weighing more than 66 lb and 0.15 mg for those weighing between 33 lb and 66 lb.7 Patient resources detailing the identification, treatment, and management of anaphylaxis are available from Food Allergy Research and Education (FARE) (www.foodallergy.org/anaphylaxis, accessed January 15, 2014). A written action plan that details emergency actions should anaphylaxis occur needs to be provided to all patients with food allergy.7 A child’s school, day-care facility, and extended family members need to be aware of the emergency plan. An TABLE 3. Signs and symptoms of anaphylaxis Angioedema of conjunctiva, face, lips, mouth, tongue, or throat Cardiac—tachycardia, hypotension Central nervous system—loss of consciousness, confusion, headache, anxiety Epidermis—urticaria, pruritus, flushing Gastrointestinal—abdominal pain, diarrhea, vomiting Nasal rhinorrhea
Food allergy anaphylaxis
Anaphylaxis is a serious, generalized immune-mediated hypersensitivity reaction that may result in death if not promptly treated. The signs and symptoms of anaphylaxis vary from person to person and from reaction to reaction
Respiratory—shortness of breath, wheezing, dysphagia, cough Urinary incontinence Adapted from Sampson HA. Anaphylaxis and emergency treatment. Pediatrics. 2003;111:16011608. Available at pediatrics.aappublications.org/content/111/Supplement_3/1601.long, accessed January 15, 2014.
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