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Wise et al.

Page 153

severity of AD has been shown to correlate with an increased risk of developing AR, with prevalence of AR among people with AD ranging from 15% to 61%. 1898-1900

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The best evidence of disease association derives from studies which compare the incidence and/or prevalence of AR in populations with and without AD. In this regard, the limited evidence available suggests that AD is associated with a 2-fold increase in AR among people with AD compared with the normal population. 1901 In this study, among those children with present or past AD, 60.8% reported AR compared to 31% in subjects without AD. • Aggregate Grade of Evidence: C (Level 2b: 4 studies;, Level 3b: 15 studies; Level 4: 1 study; Table X.D). Approximately 5% to 8% of patients with pollen allergy will develop food allergy and pollen-food allergy syndrome (PFAS). 1916 Patients with pollen allergies may have allergy related manifestations after consuming specific fruits, vegetables, nuts, or spices. The prevalence of pollen-food allergies varies with the type of pollen. As many as 70% of patients with birch allergy will manifest a food-related sensitivity. 1917 PFAS is an IgE mediated reactivity, which occurs in the oral mucosa, leading to itching, stinging pain, angioedema, and rarely systemic symptoms. The term, “oral allergy syndrome” (OAS), has also been frequently used and refers to a pollen-food allergy that occurs only at the level of the oral mucosa. OAS is, therefore, a specific manifestation of the broader PFAS. The symptoms of OAS manifest because of IgE specific for the offending pollen cross-reacting with highly homologous proteins found in a variety of fruits, vegetables, and nuts. The most common example of this cross-reactivity in western populations is birch pollen and apples. Table X.E-1 lists common pollen allergens with plant-derived foods that may demonstrate cross-reactivity. These pollen-food relationships have been observed clinically and are also demonstrated at a molecular level through identification of the homologous amino acids, cross-reactive carbohydrate determinants, and lipid transfer proteins. The birch-apple syndrome is due to the high homology of the major birch allergen Bet v 1 and the apple allergen Mal d 1. 1918 The diagnosis of PFAS is typically established by a detailed history and physical exam. The history should be guided by an understanding of the patient’s underlying pollen allergy and foods that share highly homologous proteins. The clinician should elicit a detailed history of the allergic response including any systemic symptoms and history of anaphylaxis. The estimated rate of systemic reaction from a pollen-food allergy is 10% and the estimated rate of anaphylaxis is 1.7% to 10%. 1742,1919,1920 Systemic symptoms are the manifestation of an allergic response by organ systems that have not come into direct contact with the ingested food and include: urticaria, nasal congestion, sneezing, flushing, wheezing, cough, diarrhea, and hypotension. The gold standard for establishing a diagnosis of PFAS is a double-blind food challenge. However, this is difficult to perform because of the bias inherent to the appearance, texture, and taste of foods. 1921 Oral food challenge, SPT, and food-specific IgE levels have also been used to establish the diagnosis. The diagnostic approach should be guided by the patient’s history and severity of allergic response.

X.E. Food allergy and pollen-food allergy syndrome (PFAS)

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.