CHAPTER 18 | Food Allergy and Adverse Food Reactions in Older Adults 269 Oral Food Challenges


In some cases, a physician may order an oral food challenge (OFC) to verify the results of a SPT or blood test, assess tolerance in individuals with known food allergy, determine whether foods are triggering con- current conditions (eg, EoE or atopic dermatitis), or assess the tolerance of a trigger food in another form (eg, baked milk or egg).7


The main goals of an OFC


are as follows: (1) to identify and diagnose a food allergy or (2) to confirm tolerance in order to expand the diet, as unnecessary or numerous dietary restric- tions can lead to nutritional deficiencies. The OFC is considered the gold standard for diagnosis because the physician can see reactions in real time. The OFC can be administered in three ways:


• Open: This is the most common method in the traditional clinical setting, where both the older adult and the physician are aware of the food being evaluated.


• Blinded: With this method, the individual is unaware whether the food being tested is the trig- ger food or a placebo.


• Double-blinded, placebo-controlled challenge: This method follows the strictest guidelines and is typically reserved for research settings.


During an OFC, a physician or nurse will provide the individual with a small amount of the trigger food and observe them for 15 to 20 minutes for a reaction. If no reaction occurs, the physician or nurse will offer the individual a larger dose at regular intervals until a cumulative dose equivalent to an age-appropriate serving of the food is consumed.7


If a reaction occurs,


the test is stopped immediately and appropriate med- ical treatment is administered. If no reaction occurs during the OFC, then the food should be added to the individual’s diet at regular intervals. If a reaction occurs, then the individual must continue to avoid the trigger food. A severe allergic reaction is a risk involved with OFCs, which is why these challenges must be con- ducted under medical supervision. Some older adults may choose to avoid OFCs because they can be stressful and anxiety inducing; the symptoms are sim- ilar to that of an allergic reaction, such as increased heart rate or difficulty breathing.7


However, without an OFC, it may be harder to make a clear diagnosis.


Unreliable and Unproven Diagnostic Tests


Some procedures, such as immunoglobulin G (IgG) testing, electrodermal testing, cytotoxic testing, prov- ocation or neutralization, and applied kinesiology, have been largely unproven and may lead to unnec- essary elimination diets. Several studies have demon- strated that food-specific IgG production is the body’s natural response to a regularly ingested food. A pre- vious study reported that IgG to cow’s milk protein can be detected in 98% of healthy children by age 2 years.8


Following these results without considering


the whole picture may result in unnecessary food avoidance, induce stress and anxiety for individuals and families, and lead to nutritional deficiencies.


Putting It All Together


Allergists are the most qualified practitioners to review the OFC results, as primary care practitioners (eg, general practitioners) may not have the experi- ence or training to interpret them. Ordering general food allergy panels is not helpful for the individual or their physician. Even food-specific blood tests and SPTs can have unreliable results and should only be considered as one part of the picture when diagnos- ing food allergy. A systematic review reported that SPT and IgE appear sensitive, although not specific, for diagnosing IgE-mediated food allergy.9


Because


these tests can show false-positive results, they can lead to the unnecessary food avoidance, increased anxiety, limited food choices, nutritional deficiencies, and lower quality of life.


Other Adverse Reactions to Foods


Eosinophilic Esophagitis


EoE is a chronic, immune antigen–mediated dis- ease characterized clinically by symptoms related to esophageal dysfunction and histologically by eosinophil-predominant inflammation.10


In adults,


EoE signs and symptoms include dysphagia and food impaction. Esophagogastroduodenoscopy is the stan- dard approach for diagnosing EoE.11


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