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With the incidence of food allergies continuing to go up, understanding the diagnostic process and available treatment is important.
Approximately 8% of children and adolescents in the United States have food allergies, and the incidence continues to grow.1 Between 1997 and 2007, food allergies increased by 18% in individuals 18 years or younger,2 and in 2006, 88% of schools had at least 1 student with a food allergy.3 Food allergies can develop in individuals at any age, although many develop during childhood. Milk, eggs, peanut, tree nuts, fish, shellfish, soy, and wheat make up approximately 90% of food allergies in the United States. The National Institute of Allergy and Infectious Diseases (NIAID) defines food allergy as "adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food."1
When assessing patients for food allergies, the pediatrician should remember that patients reporting a food allergy are far more common than challenge-confirmed food allergy, that food allergies are more common in children and those with atopic diseases, and that a small number of foods account for the great majority of food allergies.4
Patients are frequently referred to pediatric allergists due to concern that a food might have caused a particular set of symptoms. Common complaints include rash, rhinitis, itchy mouth, loose stools, and/or abdominal pain. It is important to realize that imunoglobulin E (IgE)-mediated food allergy will almost always elicit a response within 2 hours after food ingestion and is reproducible when that type of food is consumed again. For instance, if a rash develops when a patient drinks milk, then a thorough dietary history should include what other types of dairy the patient consumes. If the patient is eating cheese, yogurt, or ice cream without symptoms, then milk allergy can be eliminated from the differential diagnoses.
Another typical situation is confusion around lactose intolerance and milk allergy. If a patient can tolerate lactose-free cow milk, they are not allergic because the milk protein is still present. A reaction consisting of hives, swelling, vomiting, severe abdominal pain, coughing, wheezing, and other IgE-mediated symptoms is concerning for true food allergy. It is important that patients with a history of a reaction concerning for food allergy see an allergist promptly, especially when milk or egg is presumed to be the culprit. These patients often can tolerate extensively baked products that have milk or egg as ingredients.
Patients also are commonly referred for consultation following food exposure with complaints of rhinitis. There are no published studies of food allergy presenting with rhinitis symptoms alone. There is no evidence of IgE-mediated food-induced rhinitis symptoms without anaphylaxis with whole-body symptoms (ie, hives, difficulty breathing, or diarrhea); therefore, there is no indication to test for food allergens in patients presenting with rhinitis symptoms.5 Furthermore, there is no reason to eliminate a food a child has been eating and tolerating regardless of specific IgE level or skin prick test results.
Serum IgE levels for an indiscriminate panel of foods should never be drawn when evaluating food allergy. A thorough history that includes foods ingested, timing of symptom onset in relation to the food, symptoms, symptom duration, and subsequent exposure to the food should be obtained. If the patient has been able to tolerate a normal amount of the food following the reaction, food allergy can be eliminated. The misinterpretation of IgE levels often leads to the inappropriate avoidance of a food, which may lead to the development of true IgE-mediated food allergy. Although food-specific IgE levels and skin prick testing can be useful, it is important to recognize that the gold standard for determining if a patient has a true food allergy is ingestion of the food. If it is tolerated without reaction, there is no food allergy and any positive testing results are false positives.
Social media has had positive and negative aspects in the realm of food allergy. Social media allows patients and families to connect with one another to share their experiences, swap recipes geared toward those with food allergies, and find support. However, it also allows for open discussion of food allergy and food sensitivity in which information presented might not be evidenced based or accurate. Advertising for IgG (not IgE) testing has led to inappropriate food allergy testing and unnecessary food avoidance. IgG is a marker of exposure, and one would not be surprised to find that foods that are routinely consumed have detectable IgG values. An elevated IgG value has no role in diagnosing food allergy. IgE or skin prick testing is used to bolster the evidence that there was a particular food responsible for the symptoms that are compatible with allergy; it cannot be used by itself to make the diagnosis of a food allergy. The overuse of serum IgG testing for dietary guidance can lead to unnecessary avoidance of foods, which may lead to nutritional deficient dietary practices, a big concern in a growing child.
Perhaps the newest breakthrough in the area of food allergy over the past year has been the US Food and Drug Administration approval of Palforzia, an oral immunotherapy product aimed at reducing the severity of reactions to peanut exposure among individuals with a peanut allergy. Although there are allergists across the United States who offer oral immunotherapy for various foods, these are typically not covered by insurance and cost can be a barrier. Whereas Palforzia is not a cure for peanut allergy and does not allow an individual to eat peanut ad lib, it is another option for managing food allergies. With the advancements over the past few years in food allergy, such as recommendations about early peanut introduction in infants at higher risk of developing peanut allergy, patients should be evaluated by an allergist who keeps abreast of the latest developments in the field.
1. Boyce J, Assa’ad A, Burks AW, et al; NIAID-Sponsored Expert Panel. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel. J Allergy and Clin Immunol. 2010;126(suppl 6):S1-S58. doi:10.1016/j.jaci.2010.10.007
2. Branum AM, Lukacs S. Food allergy among U.S. children: trends in prevalence and hospitalizations. NCHS Data Brief. 2008;(10):1-8.
3. O’Toole TP, Anderson S, Miller C, Guthrie J. Nutrition services and foods and beverages available at school: results from the School Health Policies and Programs Study 2006. J Sch Health. 2007;77(8):500-521. doi:10.1111/j.1746-1561.2007.00232.x
4. Sampson HA, Aceves S, Bock SA, et al. Food allergy: A practice parameter update—2014. J Allergy Clin Immunol. 2014;134(5):1016-1025. doi:10.1016/j.jaci.2014.05.013
5. Dykewicz MS, Wallace DV, Amrol DJ, et al. Rhinitis 2020: A practitioner parameter update. J Allergy Clin Immunol. 2020;146(4):721-767. doi:10.1016/j.jaci.2020.07.007