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Like all food allergies, diagnosing an allergy to soy starts with a physical examination and, of critical importance, a food-allergy-focused patient history.7,8
The findings of this patient history can then be used to guide testing decisions and results interpretation. This systematic approach can help determine whether the reported history of food allergy, combined with laboratory data such as specific IgE testing, is sufficient to diagnose soy allergy or determine whether an oral food challenge should be considered.9
Identifying individuals with soy allergy is important, as many processed foods contain soy.2 Soy protein is one of the most common pediatric food allergens, and is also an important source of nutrition for infants with a cow’s milk allergy.2 Therefore, soy avoidance is challenging for patients with soy allergy.2
Isolated soy allergy seems to be a rare occurrence; for example, according to one study, 88 percent of children with soy allergies also have peanut allergies.1 Plus, about 6 percent of atopic children and 10 percent to 14 percent of infants with a cow's milk allergy also suffer from concomitant soy allergy. 1
The evaluation for a patient with a possible food allergy begins with a thorough history and physical exam. If the clinical history suggests an IgE-mediated food allergy, skin-prick or specific IgE tests are needed to help confirm the diagnosis.
Food allergy, including soy allergy, and can have a dramatic effect on quality of life.11 Many studies have detailed the negative effect of food allergy on health-related quality of life (HRQoL), as well as the financial and emotional toll a food allergy takes.9 Identified issues include feeling different because of the diet, worrying about foods, the presence of physical and emotional distress, increased responsibility, effect on social activities (social restrictions, school, travel, and dining out), anxiety, stress, bullying, and having to consistently exercise greater caution.9
Soy is so widely distributed in processed foods that avoidance of soy is very difficult.12 Because of the nearly unlimited uses of soy, it is a particularly insidious hidden allergen.12
Soy can be used in the manufacture of food in a great variety of ways, including as a “texturizer,” emulsifier, and protein filler.12 The majority of breads contain some soy flour and so may pastries, cakes, biscuits, and baby foods.12 It is also used in the manufacture of sausages, processed meats, hamburgers, and other meat products.12 And soy is a popular vegetarian meat substitute in vegetarian products and in catering establishments, including hospital and army food services, and feeding programs.2,12 Other foods that may contain soy include pureed and cereal baby foods, and margarine. 12
Adding diagnostic testing to aid in a differential diagnosis has been shown to increase confidence in diagnosis to 90 percent.i,ii Conventionally, a diagnosis of allergic or autoimmune disease relies on the case history and a physical examination. However, adding diagnostic testing to aid in a differential diagnosis has been shown to increase confidence in diagnosis.i,ii Diagnostic testing can also help to improve the patient’s quality of life and productivity, reduce costs associated with absenteeism, and optimize use of medication, in addition to decreasing unscheduled healthcare visits.iii,iv
i. Duran-Tauleria E, Vignati G, Guedan MJ, et al. The utility of specific immunoglobulin E measurements in primary care. Allergy. 2004;59 (Suppl78):35-41.
ii. NiggemannB, Nilsson M, Friedrichs F. Paediatric allergy diagnosis in primary care is improved by in vitro allergen specific IgE testing. Pediatr Allergy Immunol. 2008;19:325-331
iii. Welsh N, et al. The Benefits of Specific Immunoglobulin E Testing in the Primary Care Setting. J Am Pharm Assoc. 2006;46:627.
iv. Szeinbach SL, Williams B, Muntendam P, et al. Identification of allergic disease among users of antihistamines. J Manag Care Pharm. 2004; 10 (3): 234-238
Strict avoidance of the allergenic food is the cornerstone of management for individuals with food allergy, including soy.13 While this is seemingly straightforward, adhering to strict avoidance may be challenging as soy is frequently hidden in foods.12,13
Keeping a patient with soy allergy safe is contingent on frequent label reading, preventing cross-contact, providing anticipatory guidance to caregivers regarding reaction severity and treatment, and the patient or caregivers effectively communicating with restaurant staff when eating outside of the home.13 Label reading alone requires constant vigilance due to changing manufacturing practices over time.13
Practice parameters have been developed to help guide the management and treatment of patients with food allergies, including soy.