A retrospective study of peanut and tree nut allergy: Sensitization and correlations with clinical manifestations

Allergenicity of peanut allergens and its dependence on the structure

Food allergies are a global food safety problem. Peanut allergies are common due, in part, to their popular utilization in the food industry. Peanut allergy is typically an immunoglobulin E-mediated reaction, and peanuts contain 17 allergens belonging to different families in peanut. In this review, we first introduce the mechanisms and management of peanut allergy, followed by the basic structures of associated allergens. Subsequently, we summarize methods of epitope localization for peanut allergens. These methods can be instrumental in speeding up the discovery of allergenicity-dependent structures. Many attempts have been made to decrease the allergenicity of peanuts. The structures of hypoallergens, which are manufactured during processing, were analyzed to strengthen the desensitization process and allergen immunotherapy. The identification of conformational epitopes is the bottleneck in both peanut and food allergies. Further, the identification and modification of such epitopes will lead to improved strategies for managing and preventing peanut allergy. Combining traditional wet chemistry research with structure simulation studies will help in the epitopes' localization.

Patterns of Clinical Reactivity in a Danish Cohort of Tree Nut Allergic Children, Adolescents, and Young Adults

Background

Tree nut allergy is associated with severe reactions and poly-sensitization to other nuts and peanuts often occurs. There are regional differences in sensitization profiles that result in differences in clinical presentation. Denmark is located in a birch pollen endemic area, which could influence the allergy patterns due to pollen cross-sensitization.

Objective

This study aimed to investigate patterns of sensitization and clinical reactivity to tree nuts and peanuts and threshold levels for oral food challenges (OFCs) in a Danish cohort of tree nut allergic children, adolescents, and young adults.

Methods

Forty tree nut allergic subjects were assessed for clinical reactivity to six nuts, i.e., hazelnut, walnut, pistachio, cashew, almond, and peanut, by OFCs or convincing medical history of an immediate allergic reaction or tolerance. Clinical presentation and allergen-specific immunoglobulin E (sIgE) levels together with eliciting dose and rescue medication in OFCs were furthermore assessed.

Results

Allergy to two or more tree nuts was observed in most cases. Hazelnut-walnut dual allergy was common but not exclusively observed as concomitant allergies. Allergy to cashew was coincided in all but one of the assessed subjects with pistachio allergy. Half of all assessed subjects were allergic to peanuts. Oral symptoms followed by a skin reaction were the most common symptomatology that lead to OFC cessation and subjects often presented with symptoms from two or more organ systems. OFC threshold levels were within the same range, but cashew was distinguished from other nuts by causing allergic symptoms at the lowest dose. Clinical reactivity and the allergy patterns were to some extent reflected by sIgE levels and by correlations in sIgE between the nuts.

Conclusions

In this Northern European cohort, subjects with clinically relevant tree nut allergy were generally allergic to two or more tree nuts and close to half of them also to peanuts. There were two distinct and independent allergic phenotypes; the majority of hazelnut allergic subjects were also allergic to walnut, and all but one subject with cashew allergy were dual allergic to pistachio. These findings are consistent with a strong sIgE correlation between hazelnut and walnut and a close to total sIgE correlation between cashew and pistachio.

Tree nut introduction in a peanut-allergic child: To eat, to screen, or to avoid?

There is no defined standard of care around tree nut introduction in a peanut-allergic child, and the role of screening prior to tree nut introduction is controversial. There is some evidence that peanut-allergic children are at increased risk of tree nut allergy, with approximately 23-68% of children with co-existent peanut/tree nut allergy. In some studies, it has been shown that tree nut allergy in children has the potential to be a severe allergy. However, this appears to be age-specific as infant anaphylaxis in general tends to be milder, and there has been no fatality reported on the first ingestion of an allergen in infancy. Familial hesitancy has been identified as a possible condition for undertaking screening tests prior to allergen introduction. Indeed, there has been limited evidence that caregiver hesitancy may exist in peanut-allergic families with tree nut introduction. However, pre-emptive screening has the potential to overdiagnose tree nut allergy and delay introduction (which could paradoxically increase risk). As a result, the decision is best made in the context of shared decision-making and patient preference-sensitive care.

The global burden of illness of peanut allergy: A comprehensive literature review

Peanut allergy (PA) currently affects approximately 2% of the general population of Western nations and may be increasing in prevalence. Patients with PA and their families/caregivers bear a considerable burden of self‐management to avoid accidental peanut exposure and to administer emergency medication (adrenaline) if needed. Compared with other food allergies, PA is associated with higher rates of accidental exposure, severe reactions and potentially fatal anaphylaxis. Approximately 7%–14% of patients with PA experience accidental peanut exposure annually, and one‐third to one‐half may experience anaphylaxis, although fatalities are rare. These risks impose considerably high healthcare utilization and economic costs for patients with PA and restrictions on daily activities. Measures to accommodate patients with PA are often inadequate, with inconsistent standards for food labelling and inadequate safety policies in public establishments such as restaurants and schools. Children with PA are often bullied, resulting in sadness, humiliation and anxiety. These factors cumulatively contribute to significantly reduced health‐related quality of life for patients with PA and families/caregivers. Such factors also provide essential context for risk/benefit assessments of new PA therapies. This narrative review comprehensively assessed the various factors comprising the burden of PA.

Recent advances in the management of nut allergy

Peanut/tree nut allergy is common and has been associated with particularly severe reactions. Epidemiological data have shown that the prevalence ranges between 0.05% and 4.9% for tree nut and between 0.5% and 3% for peanut. These large variations can be explained by differences in the age of included patients and the geographical region. In addition, the food consumption modality (ie, raw versus roasted) plays a major role, as heat treatment has the capacity to modify the allergenicity of nuts and legumes. Nut allergies tend to persist into adulthood and consequently have a high impact on quality of life.

Recently, it has been demonstrated that a significant proportion of nut allergic patients are able to tolerate other nuts. As opposed to the avoidance of all nuts, this approach is currently proposed in several tertiary allergy centers. However, diagnosis of nut allergy is particularly difficult due to co-sensitization leading to high rate of false positive skin prick tests and/or specific IgE to whole allergen extracts. The use of component resolved diagnosis leads to major improvement of diagnosis, particularly to distinguish between primary and secondary nut allergies. The basophil activation test has been suggested to be useful but is still used mainly as a research tool. Thus, diagnosis remains mainly based on the oral food challenge, which is considered as the gold standard.

Regarding treatment, avoidance remains the cornerstone of management of nut allergy. Oral immunotherapy is increasingly proposed as an alternative management strategy.

A 5-year retrospective review of children with peanut allergy in the largest paediatric hospital in Singapore

Background

The prevalence of peanut allergy (PA) among children has increased significantly over the past decade. Even though the prevalence of PA in Singapore is considered low, peanut is the top trigger for food-induced anaphylaxis in Singaporean children.

Objective

To describe the demographic characteristics and clinical features of children with PA.

Methods

This is a 5-year retrospective review of children diagnosed with PA based on clinical history coupled with a positive skin prick test to peanut or positive oral food challenge results.

Results

There were 269 patients (53.9% males) with a clinical diagnosis of PA. The median age at first allergic presentation for the PA group was 24 months old, with interquartile range of 13-39 months. The most common form of peanut introduced was roasted peanut. The rate of peanut anaphylaxis was 7.1%. Concomitant tree nut sensitization was found in 32.3% of this cohort, predominantly to cashew nut. Majority of them have a personal history of atopy - 75.8% with eczema, 63.6% with allergic rhinitis, and 19.7% with asthma.

Conclusion

This is the first large review of peanut-allergic children in Singapore. Prospective population-based studies are needed to establish the true prevalence and risk factors associated with the development of this potentially life-threatening condition.

Allergen-Specific Immunotherapy for Immunoglobulin E-Mediated Food Allergy

Food allergy is a potentially life-threatening condition and a significant public health concern worldwide. The current management includes food avoidance and use of emergency medications. The growing prevalence of food allergy drives research towards specific allergen immunotherapy (AIT), which represents a potential disease-modifying approach. AIT consists of the progressive administration of amounts of the offending allergen in order to induce food desensitisation, creating an increase in reaction threshold with regular exposure to the allergen. AIT can be performed through oral, sublingual, epicutaneous, and subcutaneous routes. The target is to achieve post desensitisation effectiveness: a long-lasting condition allowing patients to introduce food without reactions, even after a period of discontinuation of the offending food.

Recent advances in understanding and preventing peanut and tree nut hypersensitivity

Peanut allergy, the most persistent and deadly of the food allergies, has become more prevalent worldwide in recent decades. Numerous explanations have been offered for the rise in peanut allergy, which has been more pronounced in Western, industrialized nations. In infants who are at increased risk of peanut allergy, new evidence indicates that early introduction of peanuts can help prevent allergy development. This counterintuitive finding directly contradicts the previously established practice of peanut avoidance for high-risk infants but is supported by clinical and basic science evidence. Here, we review the literature contributing to our evolving understanding of nut allergy, emphasizing the translation of this work to clinical practice.

Peanut Allergy: An Epidemiologic Analysis of a Large Database

OBJECTIVE

To confirm new observations on peanut allergy and answer current concerns that families and healthcare providers have about peanut allergy.

STUDY DESIGN

Children who presented with a story of peanut allergy or peanut sensitization were asked to participate in a registry, which allowed an analysis focused on questions that a food allergy support group had about children with peanut allergy or sensitization.

RESULTS

A total of 1070 children were entered into the registry over 5 years. Two-thirds had a reaction to peanut. Children with peanut allergy were predominantly male (63%), white (78%), and with private health insurance (80%). Most reactions involved the skin (55%) and anaphylaxis occurred in 35%. The median age of a reaction was 1 year old. Atopic dermatitis was noted in 60% and asthma in 41%. Additional food allergy was noted in 58%. When second exposures occurred 28% had a more severe reaction. Skin test size did not differentiate the type of a reaction and children with anaphylaxis had slightly higher specific IgE levels. Severe reactions with inadvertent exposure in children who were peanut sensitized was rare (<1%).

CONCLUSIONS

The strategies for peanut allergy prevention and treatment have evolved. The data obtained in this large registry can answer many questions that families and healthcare providers have during this transition.