Elimination diet and the development of multiple tree-nut allergies.

BackgroundDespite its high prevalence, relatively little is known about the characteristics of patients with multiple tree-nut allergies.MethodsPatients (n=60, aged 4-15 years), recruited for a multiple food (tree nuts, peanut, milk, egg, soy, sesame, and wheat) oral immunotherapy (OIT) study, filled a questionnaire on their initial allergy evaluation. Medical records were reviewed. At OIT enrollment (median interval, 7.5 years), patients underwent oral food challenges (OFCs) to foods still eliminated.ResultsThere was significantly less evidence for eliminating tree nuts compared with other foods, as reflected by a lower rate of acute reaction to the offending food, either as the trigger for initial allergy evaluation (5.9% for tree-nuts vs. 20-40% for other foods, respectively P<0.001) or later in life (14.5% vs. 38-75%, respectively P=0.001), and a higher rate of negative skin prick test (SPT)/specific IgE (sIgE) at initial diagnosis (25% vs. <10%, P<0.001). SPT/sIgE increased significantly from past initial levels to present for tree nuts (P<0.001) and peanut (P=0.001) but not for other foods, and most OFCs performed at present were positive.ConclusionsTree nuts are often eliminated from the diet of multiple-food-allergic patients, despite their low probability for allergy. Sensitization and allergy to most tree nuts exist years later, suggesting that it developed during the period of elimination.

Threshold Dose Distribution in Walnut Allergy.

BACKGROUND: In food allergy, eliciting doses (EDs) of foods on a population level can improve risk management and labeling strategies for the food industry and regulatory authorities. Previously, data available for walnut were unsuitable to determine EDs. OBJECTIVE: The objective of this study was to determine EDs for walnut allergic adults and to compare with previously established threshold data for peanut and tree nuts. METHODS: Prospectively, adult subjects with a suspected walnut allergy underwent a low-dose double-blind, placebo-controlled food challenge. Individual no observed and lowest observed adverse effect levels were determined and log-normal, log-logistic, and Weibull models were fit to the data. Estimated ED values were calculated for the ED5, ED10, and ED50, the dose respectively predicted to provoke an allergic reaction in 5%, 10%, and 50% of the walnut allergic population. RESULTS: Fifty-seven subjects were challenged and 33 subjects were confirmed to be walnut allergic. Objective symptoms occurred in 20 of the positive challenges (61%). The cumulative EDs in the distribution models ranged from 3.1 to 4.1 mg for the ED05, from 10.6 to 14.6 mg walnut protein for the ED10, and from 590 to 625 mg of walnut protein for the ED50. CONCLUSIONS: Our data indicate that population EDs for walnut are slightly higher compared with those for peanut and hazelnut allergy. Currently available data indicate that the ED values for hazelnut could be used as a conservative temporary placeholder when implementing risk management strategies for other tree nuts where little or no food challenge data are available.

Managing Nut Allergy: A Remaining Clinical Challenge.

Peanut and tree nut allergies have become a public health problem over the last 2 decades. The diagnostic procedure relies on a suggestive history, as well as on evidence of sensitization (skin prick testing and/or specific IgE blood testing), followed in selected cases by a food challenge. Standard IgE tests may be positive to more than 1 nut, due to cross-reactivity (allergens common to several nuts) or cosensitivity (frequently associated positive test results without cross-reactivity). Thus, many patients with a peanut or a tree nut allergy avoid all nuts, relying on positive test results without clinical evidence of reactivity. In addition, coexisting pollen sensitivity may add to diagnostic uncertainty due to potential cross-reactivity between pollens and nuts. In this article, we discuss challenges in diagnosis and clinical management of peanut and tree nut allergy related to cross-reactivity and cosensitization, as well as the avoidance of nuts tested positive to reduce the risk of reactions by cross-contamination. Studies to provide more accurate characterization of genuine clinically relevant cross-reactivity or cosensitivity to multiple nuts are needed.

Single nut or total nut avoidance in nut allergic children: outcome of nut challenges to guide exclusion diets.

BACKGROUND: Children with diagnosed nut allergy are typically advised by health professionals to exclude all nuts from their diets, irrespective of the outcome of allergy testing, to avoid inadvertent contact through contamination or the possible development of new allergies. METHODS: In our service, as we feel greater diagnostic accuracy prevents dietary risk taking, we provide the facility for children with nut allergy the opportunity of controlled exposure to 'other' nuts irrespective of whether their allergy prick test (PT) results are positive or negative. We performed open food challenges on our paediatric day ward. The challenge food was administered by way of a homemade biscuit containing 8 g of each nut challenged and given in increasing visually measured doses. RESULTS: Over the 5-year period from 2006, we challenged 145 children diagnosed as peanut allergic or tree nut allergic. In those with peanut allergy challenged to tree nuts, none of the 72 with negative PTs to tree nuts reacted on challenge whilst 7 of 22 (31.2%) with positive PTs did. In patients with tree nut allergy challenged to peanuts and/or other tree nuts, 3 of 38 (7.9%) with negative PT results and 5 of 13 (38.4%) with positive PT results reacted. CONCLUSION: Children allergic to peanuts with negative allergy tests to tree nuts had no co-existing allergy, but were at risk of tree nut allergy where PTs were positive. Children with tree nut allergy were at risk of co-existing peanut or other tree nut allergy whether PTs were positive or negative. Oral challenges to clarify allergy status in all nuts show co-existing allergies even in young children and in so doing may reduce anxiety, minimize unnecessary dietary restrictions and prevent later episodes of anaphylaxis through uninformed exposure.

[Allergy to cashew nuts and peanuts]. / Allergie voor cashewnoten en pinda's.

Anaphylaxis due to the ingestion of peanuts is a serious, common condition, known to both the general public and physicians. Recently, an increasing number ofpatients with an anaphylactic reaction after eating small amounts of cashew nuts have been reported. In three children, a boy aged 7 and two girls aged 9 and 10 years, respectively, with heterogeneous case histories involving allergic upper airway and conjunctival symptoms and constitutional eczema, allergy for cashew nuts was diagnosed in the first two and allergy for peanuts in the third. They were given dietary advice and an adrenaline auto-injector for emergencies. In most cases, a detailed food history, together with the demonstration of IgE against cashew nuts by means of serology or skin prick tests, are sufficient to establish the diagnosis. If the clinical relevance of a sensitisation to cashew nuts is unknown, a food provocation test may be necessary. The treatment consists of dietary intervention, and an adrenaline auto-injector is prescribed for a serious anaphylactic reaction. So far, three major allergens from the cashew nut (Anacardium occidentale) have been identified and purified.