Rising prevalence of allergy to peanut in children: Data from 2 sequential cohorts

Oral immunotherapy for food allergy

Current management of food allergy involves strict avoidance, education on recognizing and managing allergic reactions, and carrying an adrenaline autoinjector. This approach is burdensome and associated with reduced quality of life. Patients with food allergy would benefit greatly from a treatment that could achieve desensitization or long-term tolerance. Recent studies have shown that oral immunotherapy (OIT) can induce desensitization and modulate allergen-specific immune responses; however, it remains uncertain whether OIT can induce long-term tolerance. Nevertheless, successful desensitization provides a major advance in management by reducing the risk of reaction to low amounts of allergen. Allergic reactions during OIT are common, although severe reactions are less common. Therefore, OIT should be performed in specialist centers under close medical supervision and would ideally be conducted as part of ongoing research studies. OIT holds promise as a novel approach to managing food allergy.

Allergen-specific antibody and cytokine responses, mast cell reactivity and intestinal permeability upon oral challenge of sensitized and tolerized mice

BACKGROUND

Food allergy has reached an epidemic level in westernized countries and although central mechanisms have been described, the variability associated with genetic diversity underscores the still unresolved complexity of these disorders.

OBJECTIVE

To develop models of food allergy and oral tolerance, both strictly induced by the intestinal route, and to compare antigen-specific responses.

METHODS

BALB/c mice were mucosally sensitized to ovalbumin (OVA) in the presence of the mucosal adjuvant cholera toxin, or tolerized by intra-gastric administrations of OVA alone. Antibody titres and cytokines were determined by ELISA, and allergic status was determined through several physiologic parameters including decline in temperature, diarrhoea, mast cell degranulation and intestinal permeability.

RESULTS

OVA-specific antibodies (IgE, IgGs and IgA in serum and feces) were produced in sensitized mice exclusively. Upon intra-gastric challenge with OVA, sensitized mice developed anaphylactic reactions associated with a decline of temperature, diarrhoea, degranulation of mast cells, which were only moderately recruited in the small intestine, and increased intestinal permeability. Cytokines produced by immune cells from sensitized mice included T-helper type 2 cytokines (IL-5, IL-13), but also IL-10, IFN-gamma and IL-17. In contrast, all markers of allergy were totally absent in tolerized animals, and yet the latter were protected from subsequent sensitization, demonstrating that oral tolerance took place efficiently.

CONCLUSION

This work allows for the first time an appropriate comparison between sensitized and tolerized BALB/c mice towards OVA. It highlights important differences from other models of allergy, and thus questions some of the generally accepted notions of allergic reactions, such as the protective role of IFN-gamma, the importance of antigen-specific secretory IgA and the role of mucosal mast cells in intestinal anaphylaxis. In addition, it suggests that IL-17 might be an effector cytokine in food allergy. Finally, it demonstrates that intestinal permeability towards the allergen is increased during challenge.

Digested Ara h 1 has sensitizing capacity in Brown Norway rats

BACKGROUND

Food allergies are a public health issue of growing concern, with peanuts in particular being associated with severe reactions. The peanut allergen, Ara h 1, belongs to the cupin plant food allergen family, which, unlike other structural families, appears to be broken down rapidly following gastrointestinal digestion.

OBJECTIVE

Using Ara h 1 as a model allergen, the ability of digested protein to sensitize has been investigated.

METHODS

Ara h 1 was purified from whole roasted peanuts. Intact Ara h 1 was digested in an in vitro model, simulating the human gastrointestinal digestion process. Digestion products were analysed for peptide sizes and their ability to aggregate. Brown Norway (BN) rats, used as an animal model, were immunized with purified intact Ara h 1 or the gastrointestinal digestion products thereof. The sensitizing capacity was evaluated by analyses of specific antibody (IgG1, IgG2a and IgE) responses and ability to trigger mediator release of rat basophilic leukaemia (RBL)-2H3 cells.

RESULTS

The present study showed that Ara h 1 was broken down, resulting in peptide fragments of sizes<2.0 kDa, of which approximately 50% was in aggregated complexes of Mr up to 20 kDa. Ara h 1 digesta were shown to have sensitizing capacity in BN rats, being capable of inducing specific IgG and IgE antibodies. The IgE response was functional, having the capacity to induce specific degranulation of RBL cells.

CONCLUSION

From this study, it can be concluded that lability of a food allergen to gastrointestinal digestion does not necessarily abrogate its allergenic sensitizing potential.

Food allergy: is strict avoidance the only answer?

It is an immunological paradigm that avoidance of food allergen may reduce the risk or prevent immunological reactions and conversely that a greater exposure increases the magnitude of the immune response. Consequently, food allergen avoidance has been recommended to reduce the risk of sensitization in infants and to prevent clinical reactions in children with positive skin prick tests (SPT). In the latter setting, it is hoped that avoidance may either promote or at least not retard the development of tolerance. Animal studies, however, have demonstrated that tolerance to food allergens may be induced by either large (high zone tolerance) or small (low zone tolerance) doses, whereas doses in between may actually stimulate immune responses. In this review, we discuss whether strict allergen avoidance is always the most appropriate strategy for preventing or managing IgE-mediated food allergy.

The non-specific lipid transfer protein, Ara h 9, is an important allergen in peanut

BACKGROUND

Plant food allergy in the Mediterranean area is mainly caused by non-specific lipid transfer proteins (nsLTP). The aim of this study was to characterize peanut nsLTP in comparison with peach nsLTP, Pru p 3, and assess its importance in peanut allergy.

METHODS

Peanut-allergic patients from Spain (n=32) were included on the basis of a positive case history and either a positive skin prick test or specific IgE to peanut. For comparison, sera of 41 peanut-allergic subjects from outside the Mediterranean area were used. Natural Ara h 9 and two isoforms of recombinant Ara h 9, expressed in Pichia pastoris, were purified using a two-step chromatographic procedure. Allergen characterization was carried out by N-terminal sequencing, circular dichroism (CD) spectroscopy, immunoblotting, IgE inhibition tests and basophil histamine release assays.

RESULTS

Compared with natural peanut nsLTP, the recombinant proteins could be purified in high amounts from yeast supernatant (> or =45 mg/L). The identity of the proteins was verified by N-terminal amino acid sequencing and with rabbit nsLTP-specific antibodies. CD spectroscopy revealed similar secondary structures for all preparations and Pru p 3. The Ara h 9 isoforms showed 62-68% amino acid sequence identity with Pru p 3. IgE antibody reactivity to rAra h 9 was present in 29/32 Spanish and 6/41 non-Mediterranean subjects. Recombinant Ara h 9 showed strong cross-reactivity to nPru p 3 and similar IgE-binding capacity as nAra h 9. The two Ara h 9 isoforms displayed similar IgE reactivity. In peanut-allergic patients with concomitant peach allergy, Ara h 9 showed a weaker allergenic potency than Pru p 3 in histamine release assays.

CONCLUSIONS

Ara h 9 is a major allergen in peanut-allergic patients from the Mediterranean area. Ara h 9 is capable of inducing histamine release from basophils, but to a lesser extent than Pru p 3.

Sex Disparity in Food Allergy: Evidence from the PubMed Database

Food allergies are potentially fatal immune-mediated disorders that are growing globally. The relationship between sex and food allergy remains incompletely understood. Here we tested the hypothesis that, should sex influence the clinical response to food allergens, this would be reflected by a sex disparity in published studies of food allergy. We performed a systematic search of the PubMed literature for IgE-mediated allergy to 11 allergenic foods of international regulatory importance. No date restriction was used and only articles in English were considered. Of the 4744 articles retrieved, 591 met the inclusion criteria representing 17528 subjects with food allergies. Whereas among children with food allergies, 64.35% were males and 35.65% were females (male/female ratio, 1.80), among adults 34.82% were males and 65.18% were females (male/female ratio, 0.53). Consequently, these data argue that there is need for further investigation to define the role of sex in the pathogenesis of food allergy.

Food allergy and food sensitization in early childhood: results from the DARC cohort

BACKGROUND

The prevalence of food hypersensitivity (FHS) and the relationship with atopic dermatitis (AD) is controversial. The aim of this study was to determine the development of FHS and to correlate this with AD in relation to sensitization and symptoms.

METHODS

This study combines new data from birth to 18 months of age with previous published results from 3 and 6 years. The Danish Allergy Research Centre cohort, including 562 children, is a unique, population-based, prospective birth cohort, with clinical examinations at all follow-ups. All children were examined for the development of AD using Hanifin-Rajka criteria and for FHS using interviews, skin prick test (SPT), specific immunoglobulin E (IgE), and food challenge according to EAACI guidelines.

RESULTS

Twenty children were confirmed with FHS to milk, egg, and peanut. FHS peaked at 18 months (3.6%) and then decreased to 1.2% at 72 months of age. No new cases were found after 3 years. Self-reporting could only be confirmed in 31% of cases. Among the 122 children with AD, 18 had FHS (14.8%). FHS was IgE-mediated in 95% of the cases but 16 of 20 children were additionally sensitized to other foods which they tolerated. Children with AD were neither more IgE-sensitized nor had higher levels of IgE when compared with healthy children but they were more persistently sensitized.

CONCLUSIONS

Sensitization to foods in young children without food allergy seems to be a normal phenomenon. The discrepancy between sensitization, self-reported food-related symptoms and confirmed FHS illustrates the need to perform standardized oral challenges in order to confirm the diagnosis of FHS.

Physiological and pathophysiological functions of intestinal mast cells

The normal gastrointestinal (GI) mucosa is equipped with mast cells that account for 2-3% of lamina propria cells under normal conditions. Mast cells are generally associated with allergic disease, and indeed, food allergy that manifests in the GI tract is usually mast cell dependent. On the other hand, mast cells have a number of physiological functions in the GI tract, namely regulatory functions such as control of blood flow and coagulation, smooth muscle contraction and peristalsis, and secretion of acid, electrolytes, and mucus by epithelial cells. One of the most intriguing functions of intestinal mast cells is their role in host defense against microbes like bacteria, viruses, or parasites. Mast cells recognize microbes by antibody-dependent mechanisms and through pattern-recognition receptors. They direct the subsequent immune response by attracting both granulocytes and lymphocytes to the site of challenge via paracrine cytokine release. Moreover, mast cells initiate, by releasing proinflammatory mediators, innate defense mechanisms such as enhanced epithelial secretion, peristalsis, and alarm programs of the enteric nervous This initiation can occur in response to a primary contact to the microbe or other danger signals, but becomes much more effective if the triggering antigen reappears and antibodies of the IgE or IgG type have been generated in the meantime by the specific immune system. Thus, mast cells operate at the interface between innate and adaptive immune responses to enhance the defense against pathogens and, most likely, the commensal flora. In this respect, it is important to note that mast cells are directly involved in controlling the function of the intestinal barrier that turned out to be a crucial site for the development of infectious and immune-mediated diseases. Hence, intestinal mast cells perform regulatory functions to maintain tissue homeostasis, they are involved in host defense mechanisms against pathogens, and they can induce allergy once they are sensitized against foreign antigens. The broad spectrum of functions makes mast cells a fascinating target for future pharmacological or nutritional interventions.

The diagnosis of IgE-mediated food allergy in childhood

IgE-mediated food allergy is a common condition in childhood and a recognized public health concern. An accurate diagnosis of food allergy facilitates the avoidance of the allergen - and cross-reactive allergens - and allows for safe dietary expansion. The diagnosis of food allergy relies on a combination of rigorous history, physical examination, allergy tests [skin prick tests (SPT) and/or serum-specific IgE] and oral food challenges. Diagnostic cut-off values for SPT and specific IgE results have improved the diagnosis of food allergy and thereby reduced the need to perform oral food challenges. This clinical case series seeks to highlight a contemporary approach to the diagnosis of food allergy in children strategies.

IgE-mediated allergen gene vaccine platform targeting human antigen-presenting cells through the high-affinity IgE receptor

BACKGROUND

Treatment of IgE-mediated food allergy with standard protein-based allergen immunotherapy has proved both unsuccessful and hazardous. Allergen gene vaccination represents a promising alternative, but difficulties in gene targeting and expression in antigen-presenting cells represent a major limitation for efficient gene vaccination.

OBJECTIVE

We sought to construct a genetically engineered human epsilon-polylysine (EPL) fusion protein that binds allergen gene expression systems and targets the gene vaccine complex to antigen-presenting cells through the interaction of EPL and the high-affinity receptor for IgE for efficient allergen gene vaccination.

METHODS

Genetic engineering was used to design and produce the EPL fusion gene, consisting of the human CHepsilon2-4 linked to 55 lysine residues, and the conventional approaches were used to characterize the biologic features of EPL.

RESULTS

EPL was assembled as functional dimers and capable of binding DNA plasmids in both an EPL protein and plasmid DNA concentration-dependent manner. EPL targeted plasmid DNA to the high-affinity receptor for IgE on cell surfaces and increased the model gene uptake/expression. The EPL-DNA complexes were shown not to trigger mast cell degranulation.

CONCLUSION

EPL is able to function as a gene carrier system to target allergen gene to the high-affinity receptor for IgE-expressing cells through ligand receptor-mediated interactions.

The parent-reported prevalence and management of peanut and nut allergy in school children in the Australian Capital Territory

AIM

To describe parent-reported prevalence and management of peanut and nut allergy in school entrant children.

METHOD

A population-based, cross-sectional study in the Australian National Capital.

RESULTS

Out of 3851 children, parents reported 127 had a strong allergic reaction to peanuts and 19 to other nuts ever. Nut allergy ever prevalence was 3.8% (95% confidence interval 3.2-4.4%), and of peanut allergy ever 3.3% (2.8-3.9%). Children with nut allergy were more likely to have a general practitioner (odds ratio 2.64, 1.16-6.03), hay fever (3.78, 2.67-5.36), eczema (4.54, 3.15-6.56) and wheeze in the last 12 months (3.19, 2.22-4.59) and have been breastfed (2.68, 1.26-5.77) than those who did not. At follow up of 109 children with parent-reported allergy (75% response), 70% had diagnostic test-confirmed sensitisation, 32% had been prescribed an adrenalin autoinjector (6% had used one) and 46% were not eating peanut. Increasing severity of reported symptoms following consumption of peanut was associated with an increasing likelihood of recommended management. Based on parent report, the projected estimated diagnostic test-confirmed prevalence of peanut sensitisation was 2.4% (1.9%, 3.0%) for the entire sample.

CONCLUSION

Among a highly representative sample of children at school entry, 1 in 30 parents reported their child to have a strong allergic reaction to nuts and over 1 in 50 are estimated to have diagnostic test-confirmed peanut sensitisation, based on parent report.

Characteristics of childhood peanut allergy in the Australian Capital Territory, 1995 to 2007

BACKGROUND

It is unknown whether clinical features of peanut allergy have changed in the past decade alongside possible increasing prevalence.

OBJECTIVE

The clinical features of peanut allergy over 13 years were examined with regard to age of onset, sex distribution, severity, and incidence.

METHODS

Retrospective study of 778 patients (age 4 months to 66 years) diagnosed with peanut allergy at a community-based specialist allergy practice in the Australian Capital Territory.

RESULTS

Most peanut allergy (90%) developed by age 72 months. In this group, there were no significant time-dependent changes in sex distribution, reaction severity, or age of first reaction (mean/median 12/15.1 months). Later age of first reaction was associated with an increased risk of anaphylaxis in the overall population (P < .01) and in those with onset by 72 months, in whom risk increased by 22.7% (CI, 3.3-45.7) for every additional year of age (P < .02). Asthma was associated with increased risk of anaphylaxis (odds ratio, 1.9; P < .001). In children with peanut allergy, 22% experienced anaphylaxis with first exposure and 30% with anaphylaxis had preceding milder reactions. The estimated minimum incidences of peanut allergy and sensitization by age 72 months for children born in the Australian Capital Territory in 2004 were 1.15% and 1.53%, respectively (by end December 2007), compared with 0.73% and 0.84% for those born in 2001.

CONCLUSION

Although most characteristics of peanut allergy have changed little over the period of the last 13 years (onset age, sex, comorbidity, severity), later onset was associated with greater risk of anaphylaxis. Our data are consistent with a rise in incidence.

Peanut allergy: an overview

: Peanut allergies have been increasing in prevalence in most industrialized countries. Onset is typically in early childhood, with a trend towards earlier ages of presentation. The allergy is lifelong in most affected children, although 15-22% will outgrow their peanut allergy, usually before their teenage years. Manifestations of peanut allergy range from mild to severe, and risk factors predisposing to severe reactions are discussed. However, even in the absence of risk factors, peanut allergic individuals may still experience life-threatening anaphylactic reactions. Approaches to investigation and treatment, patterns of cross-reactivity and possible causes of rising prevalence are discussed.

Reduction of IgE binding and nonpromotion of Aspergillus flavus fungal growth by simultaneously silencing Ara h 2 and Ara h 6 in peanut

The most potent peanut allergens, Ara h 2 and Ara h 6, were silenced in transgenic plants by RNA interference. Three independent transgenic lines were recovered after microprojectile bombardment, of which two contained single, integrated copies of the transgene. The third line contained multiple copies of the transgene. Ara h 2 expression was significantly suppressed in all three lines, whereas Ara h 6 was reduced in two lines. Expression of peanut allergens Ara h 1 and Ara h 3 was not noticeably affected. Significant reduction of human IgE binding to Ara h 2 and Ara h 6 also was observed. Seed weight and germination data from transgenic and nontransgenic segregants showed no significant differences. Data collected from in vitro Aspergillus flavus infection indicate no significant difference in fungal growth between the transgenic lines and the nontransgenic controls. These data suggest that silencing Ara h 2 and Ara h 6 is a feasible approach to produce hypoallergenic peanut.

Familial aggregation of food allergy and sensitization to food allergens: a family-based study

BACKGROUND

The increasing prevalence of food allergy (FA) is a growing clinical and public health problem. The contribution of genetic factors to FA remains largely unknown.

OBJECTIVE

This study examined the pattern of familial aggregation and the degree to which genetic factors contribute to FA and sensitization to food allergens.

METHODS

This study included 581 nuclear families (2,004 subjects) as part of an ongoing FA study in Chicago, IL, USA. FA was defined by a set of criteria including timing, clinical symptoms obtained via standardized questionnaire interview and corroborative specific IgE cut-offs for > or =95% positive predictive value (PPV) for food allergens measured by Phadia ImmunoCAP. Familial aggregation of FA as well as sensitization to food allergens was examined using generalized estimating equation (GEE) models, with adjustment for important covariates including age, gender, ethnicity and birth order. Heritability was estimated for food-specific IgE measurements.

RESULTS

FA in the index child was a significant and independent predictor of FA in other siblings (OR=2.6, 95% CI: 1.2-5.6, P=0.01). There were significant and positive associations among family members (father-offspring, mother-offspring, index-other siblings) for total IgE and specific IgE to all the nine major food allergens tested in this sample (sesame, peanut, wheat, milk, egg white, soy, walnut, shrimp and cod fish). The estimated heritability of food-specific IgE ranged from 0.15 to 0.35 and was statistically significant for all the nine tested food allergens.

CONCLUSION

This family-based study demonstrates strong familial aggregation of FA and sensitization to food allergens, especially, among siblings. The heritability estimates indicate that food-specific IgE is likely influenced by both genetic and environmental factors. Together, this study provides strong evidence that both host genetic susceptibility and environmental factors determine the complex trait of IgE-mediated FA.

Advances in the treatment of peanut allergy: a case report

BACKGROUND

Peanut allergies affect 1.5% of children. The majority of reactions to peanuts are mild, but peanut allergy is also the most common cause of fatal anaphylactic reactions to food.

CASE REPORT

The purpose of this case report was to describe a 1-year old boy who developed difficulty breathing after eating a peanut food product. The boy was taken immediately by his mother to an Emergency Department, exhibiting severe respiratory distress. After speaking to the child's mother, the emergency physician (EP) realized that the wheezing was due to a peanut food allergy. The child's respiratory symptoms responded within 10 min to bronchodilatator inhalation. The EP gave the mother educational information regarding the management of asthma and the proper use of metered dose inhalers with spacer devices. The EP referred the child to a clinical allergist who specializes in the management of food allergies. The diagnosis was made by skin prick testing as well as in vitro measurement of peanut-specific immunoglobulin E.

CONCLUSION

The allergist explained that the mainstay of management of peanut allergy is avoidance of the allergenic food. Patient education involved teaching the mother to avoid high-risk situations such as dinner with family members who are not informed about the child's allergy to peanuts, encouraging the child to wear a Medic Alert Bracelet, and teaching the family and child to recognize early symptoms of allergic reactions and to manage an anaphylactic reaction, including the use of self-injectable epinephrine, as well as activating emergency services.

Maternally reported food allergies and other food-related health problems in infants: characteristics and associated factors

OBJECTIVE

Our goal was to identify the frequency, demographics, and diagnostic characteristics associated with maternally reported food allergies and other food-related health problems among infants aged < or = 1 year.

METHODS

We analyzed data from the 2005-2007 Infant Feeding Practices Study II, a longitudinal survey of 2441 US mothers of healthy singletons from pregnancy through their infant's first year. Doctor diagnosis and symptoms-based criteria were used to identify a probable-food-allergic group from maternal reports of infant health problems with food.

RESULTS

More than one fifth of the 2441 mothers reported that their infant had a food-related problem; 6% (n = 143) had a probable food allergy, and 15% (n = 359) had other food-related problems. Forty percent of the infants with a food-related health problem were evaluated by a doctor. Gastrointestinal symptoms were more commonly reported in early infancy compared with skin-related symptoms, which were reported in later infancy, and 27% received medical treatment for the symptoms. Characteristics associated with increased incidence of probable food allergy included family histories of food allergy and type 1 diabetes, gestational diabetes, living in rural or urban areas, being black, and being male. Among all infants with a food-related health problem, the majority experienced their first problem by 6 months of age. Foods recognized to be major allergens were most commonly reported as the source of an allergy.

CONCLUSIONS

Food-related problems occurred at a high frequency in the first year of life. A better understanding of the demographics, family history, disease manifestations, and diagnoses may provide insight into public health efforts to minimize or prevent food allergies in infancy and to help differentiate food-allergic problems from nonallergic food problems in this age group.

Dose-dependent food allergy induction against ovalbumin under acid-suppression: a murine food allergy model

BACKGROUND

Animal models are essential for analyzing the allergenic potential of food proteins and for investigating mechanisms underlying food allergy. Based on previous studies revealing acid-suppression medication as risk factor for food allergy induction, we aimed to establish a mouse model mimicking the natural route of sensitization in patients.

METHODS

The effect of acid-suppressing medication on murine gastric pH was assessed by intragastric pH measurements after two injections of a proton pump inhibitor (PPI). To investigate dose-dependency, mice were fed different concentrations of ovalbumin (OVA; 0.2, 0.5, 1.0, 2.5 or 5.0mg) either with or without anti-ulcer medication. Additionally, different routes of exposure (i.p. vs. oral) were compared in a second immunization experiment. Sera were screened for OVA-specific antibody titers (IgG1, IgG2a and IgE) in ELISA and RBL assay. Clinical reactivity was evaluated by measuring rectal temperature after oral challenge and by type I skin tests.

RESULTS

Two intravenous injections of PPI significantly elevated the gastric pH from 2.97 to 5.3. Only oral immunization with 0.2mg OVA under anti-acid medication rendered elevated IgG1, IgG2a and IgE titers compared to all other concentrations. Protein feeding alone altered antibody titers only marginally. Even though also i.p. immunizations induced high levels of specific IgE, only oral immunizations under anti-acids induced anaphylactic reactions evidenced by a significant decrease of body temperature.

CONCLUSION

Only low-dosage ovalbumin feedings under anti-acid medication resulted in IgE mediated food allergy. Based on this knowledge we have established a suitable food allergy model for further investigations of food adverse reactions.

Tree nut and peanut consumption in relation to chronic and metabolic diseases including allergy

The New and Emerging Research session highlighted the emerging understanding of both the positive and negative effects of nuts consumption on health. The limited nature of both experimental and epidemiological evidence for positive relationship(s) between nut intake and health were noted. Study inconsistency and limitations, particularly survey methodology, were explored. Recent results from epidemiologic studies indicating a potential negative association between nut and seed intake and cancer risk were reviewed. The ability of walnuts to reduce endothelin suggests an interesting biochemical mechanism of nut action that may affect other endothelin-associated diseases, which should be further explored. The effects of nuts and their constituents on a nuclear receptor screen (PPARalpha, beta/delta, gamma, LXRalpha, beta, RXRalpha, beta, gamma, PXR, and FXR) have been explored. Nut allergenicity and approaches necessary to minimize this effect were also described. In contrast to the positive effects, nut allergies present tree nut-allergic consumers with health challenges. The Food Allergy and Anaphylaxis Network stressed the importance of ensuring that consumers with food allergies have legible, accurate food labels. The Food Allergen Labeling and Consumer Protection Act has engendered precautionary, worst-case allergen scenario labeling statements with unknown benefits to consumer health. Issues of cross-contamination due to shared equipment and shared facilities highlighted the need to rely on allergen control programs that use ELISA technology and have increased understanding of nut allergens. Ultimately, to maximize the positive benefits of nuts, the consumer must be provided with all the information required to make an informed choice.

Food allergy overview in children

Food allergies have increased significantly in the past decade. An accurate history is crucial in approaching the management. At the outset, food intolerance must be distinguished from food allergies and, furthermore, these allergies should be classified into either an IgE, Non-IgE, or a mixed response. The clinical features vary from life-threatening anaphylaxis to milder IgE-mediated responses, atopic dermatitis, and gastrointestinal symptoms. The severity of the reaction and the potential risk for anaphylaxis on reexposure should be assessed. Milk, soy, egg, wheat, and peanut allergies are common in children, whereas peanut, tree nut, fish, shell fish allergies, and allergies to fruits and vegetables are common in adults. Structural proteins are important determinants of the severity of the reactions and may often predict the natural history and cross reactivity. Diagnostic work up must be guided by the clinical history. Skin testing and food-specific IgE done by standard methods are very useful, whereas oral challenges may be indicated in some situations. Majority of the patients outgrow their allergies to milk, soy, egg, and wheat, and some to peanut also, therefore, patients should be periodically reassessed. Novel diagnostic techniques which detect specific allergenic epitopes have been developed. Several newer therapies are promising.

New visions for basic research and primary prevention of pediatric allergy: an iPAC summary and future trends

Hydrolyzed formula feeding, delayed introduction of solid food, indoor allergen avoidance, smoke and pollutants avoidance have been applied for several decades as primary preventive measures for allergic diseases. Unfortunately, some of these strategies have had no or modest success. Therefore, resources need to be focused on better understanding of the early allergic events and on interventional studies to investigate new strategies of primary and secondary prevention. Accordingly, this review summarizes the state-of-the-art of genetic, immunological and clinical aspects of primary prevention of allergic diseases. Studies investigating gene-by-gene and gene-by-environment interactions suggest that prevention of allergic diseases must be tailored to the individual genetic susceptibilities ('gene profiling') and environmental exposures. The expanding knowledge on new T cell populations (Th17, TSLP (thymic stromal derived lymphopoietin)-dependent 'inflammatory Th2 cells') is also inspiring new concepts on the origins of allergic diseases. The old concept of 'blocking immunoglobulin G antibodies' has been re-appraised and it is likely to generate novel preventive and therapeutic strategies. The major task for future clinical research is to clearly define the timing of optimal exposure to potential allergens. In addition, the role of microbial products such as certain bacteria, or their components, and of helminths or their larvae at different times in early life, alone or with potential allergens, definitely need to be further investigated. The benefit of efficient allergy prevention, based on focusing resources on novel and promising research lines, will be of prime importance to both affluent countries and other parts of the world where allergy is only currently emerging.

A EuroPrevall review of factors affecting incidence of peanut allergy: priorities for research and policy

Peanuts are extensively cultivated around the world, providing a foodstuff that is both cheap to produce and nutritious. However, allergy to peanuts is of growing global concern, particularly given the severity of peanut-allergic reactions, which can include anaphylaxis and death. Consequently, it is important to understand the factors related to the prevalence of peanut allergy in order to inform efforts to ameliorate or pre-empt the condition. In this article we review evidence for the relevance of factors hypothesized to have some association with allergy prevalence, including both genetic and environmental factors. Although our analysis does indicate some empirical support for the importance of a number of factors, the key finding is that there are significant data gaps in the literature that undermine our ability to provide firm conclusions. We highlight these gaps, indicating questions that need to be addressed by future research.

The role of protein digestibility and antacids on food allergy outcomes

Digestion assays with simulated gastric fluid have been introduced for characterization of food proteins to imitate the effect of stomach proteolysis on dietary compounds in vitro. By using these tests, dietary proteins can be categorized as digestion-resistant class 1 (true allergens triggering direct oral sensitization) or as labile class 2 allergens (nonsensitizing elicitors). Thus the results of these digestion assays mirror situations of intact gastric proteolysis. Alterations in the gastric milieu are frequently experienced during a lifetime either physiologically in the very young and the elderly or as a result of gastrointestinal pathologies. Additionally, acid-suppression medications are frequently used for treatment of dyspeptic disorders. By increasing the gastric pH, they interfere substantially with the digestive function of the stomach, leading to persistence of labile food protein during gastric transit. Indeed, both murine and human studies reveal that antiulcer medication increases the risk of food allergy induction. Gastric digestion substantially decreases the potential of food proteins to bind IgE, which increases the threshold dose of allergens required to elicit symptoms in patients with food allergy. Thus antiulcer agents impeding gastric protein digestion have a major effect on the sensitization and effector phase of food allergy.

Food allergy-lessons from Asia

OBJECTIVE

: This is a review on published data available on food allergy in East Asia and a discussion on the insights that it offers.

METHODS

: PubMed searches were made for terms food allergy and anaphylaxis, in combination with Asia.

RESULTS

: There is a paucity of population-based prevalence studies on food allergy in Asia. Certain unique food allergens, such as buckwheat, chestnuts, chickpeas, bird's nest, and royal jelly, which are consumed extensively by certain Asian populations have resulted in clinical food allergy of little importance in other populations. Crustacean shellfish is of importance in this region relative to other common food allergens. The high consumption of these foods and possibly coupled with cross-reactive tropomyosins from dominant inhalant dust mite and cockroach allergens in this region may explain this phenomenon. In contrast, the prevalence of peanut allergy is relatively low in this region. The reasons for this difference are not apparent. However, this may be a reflection of the general reduced propensity in this region to allergic diseases as seen with asthma.

CONCLUSIONS

: Further research on food allergy in Asia is warranted because it offers unique opportunities to further our understanding on the influence of population and environment.

Epidemiologic risks for food allergy

This article reviews possible risk factors and theories for the development of food allergy. It is noted that previous strategies to prevent food allergy through allergen avoidance during pregnancy, breast-feeding, and infancy have more recently been called into question. Alternative hypotheses are examined with respect to food allergy, namely the hygiene hypothesis, the dietary fat hypothesis, the antioxidant hypothesis, and the vitamin D hypotheses. An alternative hypothesis is proposed, suggesting that sensitization to allergen occurs through environmental exposure to allergen through the skin and that consumption of food allergen induces oral tolerance. This hypothesis provides a possible explanation for the close link between eczema and the development of food allergies. It also suggests novel interventional strategies to prevent the development of food allergies.

Peanut and tree nut allergy in childhood

Peanut and tree nut allergies present multiple challenges in their presentation and management. These challenges have become increasingly relevant in recent years, as these allergies appear to have become more common. An estimated 1-2% of the population in the USA is allergic to peanut or tree nuts. Peanut allergy typically presents with symptoms in one of the first few exposures to peanut. Diagnosis is based on clinical history along with skin prick test, or quantitation of allergen-specific immunoglobulin E (IgE), and oral food challenges when indicated. Once the diagnosis is confirmed, the only current management approach is strict avoidance of the food. This is clearly an imperfect option as it can be difficult to avoid completely peanut and tree nuts and accidental exposures are not uncommon. Only about 20% of those with peanut allergy, and <10% of those with tree nut allergy, are reported to acquire tolerance. Additionally, peanut allergy can recur, with one study finding a recurrence rate of 8%. Peanut and tree nuts are the foods most frequently associated with fatal episodes of anaphylaxis. This is of particular concern in adolescents and young adults, among whom life-threatening and fatal food allergy-related reactions are most common.

Eosinophils and allergic diseases of the gastrointestinal tract

The association between increased tissue eosinophilia and allergic disease is particularly striking in the case of the gastrointestinal tract. About 80% of individuals with eosinophilic gastrointestinal disorders (EGIDs) are atopic, while half of the patients with gastrointestinal allergy show tissue eosinophilia. The function of eosinophils in gastrointestinal allergic disorders is unclear; however, a proinflammatory action is most likely. Cytokines (interleukins 5 and 3, granulocyte-monocyte colony-stimulating factor) and chemokines (eotaxin, RANTES, etc.) released by Th2 lymphocytes, mast cells and other tissue cells have been identified as major regulators of eosinophil chemotaxis and activation, but a convincing mechanism by which eosinophils are activated in an allergen-dependent manner is still lacking. The diagnostic approach comprises both histological and laboratory methods to assess eosinophilia and eosinophil activation, as well as tools to assess the allergic disease while excluding other gastrointestinal diseases such as food intolerances, infections and tumours. Treatment of allergic EGIDs includes elimination or elemental diets and drug therapy using classical anti-allergic agents such as topical corticosteroids and new approaches such as LTD4 receptor antagonists or antibodies against IL-5 or eotaxin.

The use of serum-specific IgE measurements for the diagnosis of peanut, tree nut, and seed allergy

BACKGROUND

The gold standard for diagnosing food allergy is the double-blind, placebo-controlled food challenge. Diagnostic food-specific IgE levels might assist in diagnosing food allergies and circumventing the need for food challenges.

OBJECTIVES

The purpose of this study was to determine the utility of food-specific IgE measurements for identifying symptomatic peanut, tree nut, and seed allergies and to augment what is known about the relationships among these foods.

METHODS

Patients referred for suspected peanut or tree nut allergies answered a questionnaire about their perceived food allergies. Allergen-specific diagnoses were based on questionnaire, medical history, and, when relevant, skin prick tests and serum specific IgE levels. Sera from the patients were analyzed for specific IgE antibodies to peanuts, tree nuts, and seeds by using ImmunoCAP Specific IgE (Phadia, Inc, Uppsala, Sweden).

RESULTS

Three hundred twenty-four patients (61% male; median age, 6.1 years; range, 0.2-40.2 years) were evaluated. The patients were highly atopic (57% with atopic dermatitis and 58% with asthma). The majority of patients with peanut allergy were sensitized to tree nuts (86%), and 34% had documented clinical allergy. The relationship between diagnosis and allergen-specific IgE levels were estimated by using logistic regression. Diagnostic decision points are suggested for peanut and walnut. Probability curves were drawn for peanut, sesame, and several tree nuts. High correlations were found between cashew and pistachio and between pecan and walnut.

CONCLUSIONS

Quantification of food-specific IgE is a valuable tool that will aid in the diagnosis of symptomatic food allergy and might decrease the need for double-blind, placebo-controlled food challenges.

Peanut allergy

Peanut allergy has become a major health concern worldwide, especially in developed countries. However, the reasons for this increasing prevalence over the past several decades are not well understood. Because of the potentially severe health consequences of peanut allergy, those suspected of having had an allergic reaction to peanuts deserve a thorough evaluation. All patients with peanut allergy should be given an emergency management plan, as well as epinephrine and antihistamines to have on hand at all times. Patients and families should be taught to recognise early allergic reactions to peanuts and how to implement appropriate peanut-avoidance strategies. It is imperative that severe, or potentially severe, reactions be treated promptly with intramuscular epinephrine and oral antihistamines. Patients who have had such a reaction should be kept under observation in a hospital emergency department or equivalent for up to 4 h because of the possible development of the late-phase allergic response. This Seminar looks at the changing epidemiology of this allergy--and theories as to the rise in prevalence, diagnosis, and management of the allergy, and potential new treatments and prevention strategies under development.

Prevalence and cumulative incidence of food hypersensitivity in the first 3 years of life

BACKGROUND

Prevalence and incidence of food hypersensitivity (FHS) and its trends in early childhood are unclear.

METHODS

A birth cohort born on the Isle of Wight (UK) between 2001 and 2002 was followed-up prospectively. Children were clinically examined and skin prick tested at set times and invited for food challenges when indicated.

RESULTS

Nine hundred and sixty-nine children were recruited and 92.9%, 88.5% and 91.9% of them respectively were assessed at 1, 2 and 3 years of age. Prevalence of sensitization to foods was 2.2%, 3.8% and 4.5% respectively at these ages. Cumulatively, 5.3% [95% confidence interval (CI): 3.9-7.1] children were sensitized to a food. Using open food challenge and a good clinical history, the cumulative incidence of FHS was 6.0% (58/969, 95% CI: 4.6-7.7). Based on double-blinded, placebo-controlled, food challenge (DBPCFC) and a good clinical history, the cumulative incidence was 5.0% (48/969, 95% CI: 3.7-6.5). There is no evidence to suggest that the incidence of FHS has increased, comparing these results with previous studies. Overall, 33.7% of parents reported a food-related problem and of these, 16.1% were diagnosed with FHS by open challenge and history and 12.9% by DBPCFC and history. Main foods implicated were milk, egg and peanut.

CONCLUSIONS

By the age of 3 years, 5-6% of children suffer from FHS based on food challenges and a good clinical history. There were large discrepancies between reported and diagnosed FHS. Comparing our data with a study performed in the USA more than 20 years ago, there were no significant differences in the cumulative incidence of FHS.

Factors predicting anaphylaxis to peanuts and tree nuts in patients referred to a specialist center

BACKGROUND

Although acute allergic reactions after ingestion of peanuts and tree nuts are common, fatalities are rare. Other than patients with coexisting asthma, it is currently not possible to predict which patients are most likely to develop severe reactions.

OBJECTIVE

The aim of this study was to determine which clinical and laboratory parameters best predict the likelihood of severe allergic reactions.

METHODS

From 1992 to 2004, we collected detailed information on the clinical severity and allergy test results of 1094 patients with peanut and tree nut allergy attending a regional allergy center. In a subgroup of 122 patients, sera were assayed for activity of enzymes involved in the catabolism of bradykinin.

RESULTS

Severe pharyngeal edema was 3.8 (2.1-6.9) times more common in patients with severe rhinitis and 2.6 (1.8-3.7) more common after ingestion of tree nuts compared with peanuts. Patients with serum angiotensin-converting enzyme concentrations <37.0 mmol/L had a 9.6 (1.6-57)-fold risk of severe pharyngeal edema. Life-threatening bronchospasm was most likely in patients with severe asthma (relative risk, 6.8 [4.1-11.3]) and less so in patients with milder asthma (2.7 [1.7-4.0]). Altered levels of consciousness were more likely in patients with severe eczema (3.1 [1.1-8.4]).

CONCLUSION

Severity of coexisting atopic diseases predicted which patients attending a tertiary referral clinic were most likely to develop life-threatening allergic reactions to peanuts and tree nuts. Patients with the lowest serum angiotensin-converting enzyme concentrations were more likely to develop life-threatening pharyngeal edema, suggesting that this complication may be partly mediated by bradykinin.

Reported symptoms of food hypersensitivity and sensitization to common foods in 4-year-old children

AIM

To characterize reported food hypersensitivity (FHS) among young children in a birth cohort.

METHODS

At 4 years of age a parental questionnaire on FHS and allergic symptoms was evaluated. Blood was collected for analyses of IgE-antibodies to egg, milk, fish, wheat, peanut and soy. Complete questionnaire data was available for 3694 children (90%), and blood samples were obtained from 2563 children (63%).

RESULTS

FHS was reported in 11% of the children (n=397). Eczema was the most commonly reported symptom and the only symptom in half of these children. Food-related reactions from the airways, facial oedema or urticaria were reported in 198 children, and the majority of these children (75%) reported multiple symptoms. Furthermore, a combination of airway symptoms, facial oedema or urticaria together with sensitization to food suggested a more severe form of FHS. This was found in 1.6% of all children. Symptoms caused by peanut were closely associated with sensitization to peanut (p<0.001).

CONCLUSIONS

FHS in 4-year-old children with any of asthma, rhino-conjunctivitis, facial oedema or urticaria in combination is in most cases associated to sensitization to food. This phenotype of FHS is likely to represent a more severe form of FHS.

Survey of physicians' approach to food allergy, Part 1: Prevalence and manifestations

INTRODUCTION

Food allergy (FA) prevalence is increasing and is being popularly claimed by the general population.

OBJECTIVE

To evaluate attitudinal differences between allergists and nonallergists with regard to prevalence, manifestations, offending food component, and time of onset of FA reactions.

METHODS

A 2-page questionnaire was mailed to 3,000 members of the American College of Allergy, Asthma and Immunology and 4,000 nonallergists (1,000 each of internists, pediatricians, family practitioners, and otolaryngologists).

RESULTS

Responses were received from 584 allergists and 77 nonallergists. The overall estimated prevalence of FA was significantly higher for nonallergists than allergists (12.1% vs 4.6%) and in each age group. The most common gastrointestinal manifestation of FA was oropharyngeal itching according to allergists (67.2%) vs diarrhea according to nonallergists (42.5%). More nonallergists than allergists reported neurobehavioral manifestations, musculoskeletal symptoms, and upper airway symptoms as common in FA. On the other hand, more allergists than nonallergists considered atopic dermatitis, acute urticaria or angioedema, and anaphylaxis to be common. Nonallergists considered carbohydrates, fat, and additives as causing allergy much more than allergists did (34.4% vs 6.9%; P < .001). With regard to time of onset of FA, nonallergists had higher estimates than allergists for both late (25.5.% vs 13.0%; P < .001) and delayed (22.1% vs 4.5%; P < .001) reactions.

CONCLUSION

Significant differences in attitudes toward FA were revealed between allergists and nonallergists, which highlights the need to enhance education in this area.