Macadamia nut allergy in children: clinical features and cross-reactivity with walnut
Macadamia nuts, the seeds of Macadamia tetraphylla or Macadamia integrifolia of family Proteaceae, are a familiar food item. Previous case reports of macadamia nut allergy demonstrated the possibility of false negative IgE antibody test results and cross-reactivity of macadamia nut with hazelnut. However, the clinical features of childhood macadamia nut allergy and the cross-reactivity of macadamia nut with foods other than hazelnut remain understudied.
Oral immunotherapy: The answer to peanut allergy?
Peanut and tree-nut allergies have increased dramatically in prevalence, especially in children. Historically, children with food allergies have been treated through strict avoidance of the allergen. Recently, an oral preparation of peanut allergen (Palforzia) was approved for immunotherapy (ie, desensitization) in children 4 to 17 years old. This article reviews oral immunotherapy and its role in children with peanut allergies.
Peanuts in the air clinical and experimental studies
Background: Allergic reactions to food allergens usually occur after ingestion. However, fear of reactions to airborne peanut is a common concern for people with peanut allergy. There are no scientific reports on severe reactions with airborne peanut allergen.
Objective: To investigate the occurrence of allergic reactions in peanut-allergic children undergoing airborne peanut challenge and to determine levels of airborne peanut protein in a separate experimental evaluation.
Methods: Eighty-four children with peanut allergy underwent an airborne peanut challenge; 0,5 m from a bowl of peanuts for 30 minutes under controlled conditions. In a separate experiment, airborne peanut proteins from roasted and dry-roasted peanuts was collected at varying distances and at varying times with an electret SensAbues filter connected to an air pump. Collected airborne peanut proteins were extracted, dissolved, and detected by ELISA. Basophil activation test were used to confirm biological activity.
Results: No moderate/severe allergic reactions to airborne peanut allergens were observed. Two children (2%) had mild rhino-conjunctivitis which required no treatment. The IgE-antibodies to peanut or Ara h 2 did not predict a reaction. In the experimental set-up biological active peanut proteins were detected, in a very low amount, in median 166 ng/ml for dry-roasted and 33 ng/ml for roasted peanuts and decreased dramatically when the collection occurred at a greater distance (0.5-2 m) from the peanut source. Increased exposure time did affect the amount of collected peanut protein at 0 meter, and the highest median was obtained after 60 minutes (p=0.012); for time trend p=0.0006.
Conclusions & clinical relevance: Allergic reactions to airborne peanut proteins are rare and cannot be predicted by high levels of IgE-antibodies to peanut or Ara h 2. Only small amounts of biologically active peanut proteins were detected in the air and seems unlikely to trigger moderate/severe allergic reactions.
Evaluation of the Introduction of Allergen Containing Foods: Feeding Infants and Toddlers Study (FITS) 2016
Background: Guidelines on early introduction of allergen-containing foods are evolving; however, little national data exist defining current allergen feeding practices.
Objective: To investigate consumption rates of foods containing egg and peanut among infants and toddlers prior to guideline changes in 2017.
Methods: The Feeding Infants and Toddlers Study (FITS) 2016 was conducted nationally among 3235 caregivers with a child under 4 years-of-age. 24-hr dietary recalls were reviewed for peanut or egg ingredients. Participants were categorized as "consuming peanut or egg-containing foods" or "not consuming peanut or eggcontaining foods". Data on physician-diagnosed food allergies and avoidance were collected.
Results: Consumption rates of peanut- and/or egg-containing foods were low. For the age group of 4-5.9 months, 0.3% reported peanut consumption, and 2.4% reported egg consumption. For 6-8.9 months, 0.9% reported eating peanut-containing foods and 13.0% egg, and at 9-11.9 months, 5.5% were consuming peanut-containing foods, and 33.2% egg-containing foods. Peanut or egg ingredients were identified in the diet of children whose caregivers reported avoidance.
Conclusion: Prior to publication of the 2017 Addendum Guidelines for the Prevention of Peanut Allergy, there were low rates of reported peanut consumption across the study population with < 1% of any age group prior to 9 months-of-age and < 6% in any age group prior to 12 months-of-age consuming peanut, on the 24-hour recall day. Reported egg consumption was also low and increased with age. These results serve as an important baseline comparison for future studies evaluating the implementation and impact of early peanut and egg introduction.
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.
Age and eczema severity, but not family history, are major risk factors for peanut allergy in infancy.
Background: Whether to screen high-risk groups before early peanut introduction is controversial.
Objective: We sought to determine the risk of peanut allergy (PA) before peanut introduction for infants with (1) moderate-severe eczema, (2) another food allergy (FA), and/or (3) a first-degree relative with peanut allergy (FH).
Methods: Infants aged 4 to 11 months with no history of peanut ingestion, testing, or reaction and at least 1 of the above risk factors received peanut skin prick test and, depending on skin prick test wheal size, oral food challenge or observed feeding.
Results: A total of 321 subjects completed the enrollment visit (median age, 7.2 months; 58% males); 78 had eczema only, 11 FA only, 107 FH only, and 125 had multiple risk factors. Overall, 18% of 195 with eczema, 19% of 59 with FA, and 4% of 201 with FH had PA. Only 1% of 115 with FH and no eczema had PA. Among those with eczema, older age (odds ratio [OR], 1.3; 95% CI, 1.04-1.68 per month), higher SCORing Atopic Dermatitis score (OR, 1.19; 95% CI, 1.06-1.34 per 5 points), black (OR, 5.79; 95% CI, 1.92-17.4 compared with white), or Asian race (OR, 6.98; 95% CI, 1.92-25.44) and suspected or diagnosed other FA (OR, 3.98; 95% CI, 1.62-9.80) were associated with PA.
Conclusions: PA is common in infants with moderate-severe eczema, whereas FH without eczema is not a major risk factor, suggesting screening only in those with significant eczema. Even within the first year of life, introduction at later ages is associated with a higher risk of PA among those with eczema, supporting introduction of peanut as early as possible.
Journal of Allergy and Clinical Immunology. Allergy / peanuts Ara h 2–specific IgE is superior to whole peanut extract–based serology o
Background: Screening of high-risk infants for peanut allergy (PA) before introduction is now recommended in the United States, but the optimal approach is not clear.
Objective: We sought to compare the diagnostic test characteristics of peanut skin prick test (SPT), peanut-specific IgE (sIgE), and sIgE to peanut components in a screening population of infants before known peanut exposure.
Methods: Infants aged 4 to 11 months with (1) no history of peanut ingestion, testing, or reaction and (2) (a) moderate-severe eczema, (b) history of food allergy, and/or (c) first-degree relative with a history of PA received peanut SPT, peanut-sIgE and component-IgE testing, and, depending on SPT wheal size, oral food challenge or observed feeding. Receiver-operator characteristic areas under the curve (AUCs) were compared, and diagnostic sensitivity and specificity were calculated.
Results: A total of 321 subjects completed the enrollment visit (median age, 7.2 months; 58% males), and 37 (11%) were found to have PA. Overall, Ara h 2-sIgE at a cutoff point of 0.1 kUa/L discriminated between allergic and nonallergic best (AUC, 0.96; sensitivity, 94%; specificity, 98%), compared with peanut-sIgE at 0.1 kUa/L (AUC, 0.89; sensitivity, 100%; specificity, 78%) or 0.35 kUa/L (AUC, 0.91; sensitivity, 97%; specificity, 86%), or SPT at wheal size 3 mm (AUC, 0.90; sensitivity, 92%; specificity, 88%) or 8 mm (AUC, 0.87; sensitivity, 73%; specificity, 99%). Ara h 1-sIgE and Ara h 3-sIgE did not add to prediction of PA when included in a model with Ara h 2-sIgE, and Ara h 8-sIgE discriminated poorly (AUC, 0.51).
Conclusions: Measurement of only Ara h 2-sIgE should be considered if screening of high-risk infants is performed before peanut introduction.
Prevalence of Self-Reported Food Allergies and Their Association with Other Health Conditions among Adults in Saudi Arabia.
Food allergies are a potentially life-threatening health issue, and few studies have determined their prevalence throughout Saudi Arabia. The main objective of our study was to estimate the prevalence and distribution of self-reported food allergies, and explore their association with other health conditions among adults in Saudi Arabia. This study was a nationwide cross-sectional survey conducted via phone interviews in June 2020. A proportional quota-sampling technique was used to obtain equal distributions of participants by age and gender across the 13 regions of Saudi Arabia. Self-reported food allergy, height, weight, health conditions, mental health status, and demographic variables were collected. Of the 6239 participants contacted, 4709 (75.48%) participants responded and completed the interview. Furthermore, 50.1% of the participants were female, with a mean age of 36.4 ± 13.5 years (18-90 years). The prevalence of food allergies was 19.7%. The most self-reported food allergies were egg, shellfish and shrimp, and peanuts, with a prevalence of 3.7%, 3.1%, and 3.0%, respectively. There was an association between the presence of food allergies and reported bariatric surgery, asthma, colon disease, and being at risk of depression. Bariatric surgery was significantly associated with lower likelihood of self-reported allergy (OR 1.69, 95% CI 1.22-2.34, p = 0.002). This study revealed, for the first time, a high prevalence of self-reported food allergies among adults in Saudi Arabia in a large nationwide sample, and food allergy association with bariatric surgery, asthma, colon disease, and being at risk of depression. This information is valuable for clinicians and policymakers, particularly in terms of food allergen labeling.
Mechanisms of oral immunotherapy.
Food allergy presents a significant global health concern with up to 10% of the population affected in developed nations and a steadily increasing prevalence. In many cases, particularly with peanut, tree nut and shellfish, food allergy is a lifelong and potentially life-threatening diagnosis. While no 'cure' for IgE-mediated food allergy exists, oral immunotherapy (OIT) is a promising treatment modality with the peanut OIT drug Palforzia (Aimmune Therapeutics) the only treatment for food allergy that is currently approved by the United States Food and Drug Administration. OIT primarily induces a state of desensitization with only a minority of subjects achieving sustained unresponsiveness, a state of limited clinical remission that appears to be immunologically distinct from natural tolerance. Early humoural changes during OIT include an initial increase in allergen-specific IgE, which eventually decreases to below baseline levels as OIT progresses, and a gradual increase in allergen-specific IgA and IgG4 that continues throughout the course of OIT. Basophil hyporesponsiveness and decreased skin prick test wheal size are observed within the first year of OIT, and persistence after completion of therapy has been associated with sustained unresponsiveness. In the T-cell compartment, there is an initial expansion followed by a decline in the number and activity of T helper 2 (TH 2) cells, the latter of which may be dependent on an expansion of IL-10-producing cells, including regulatory T-cells. Our understanding of the immunomodulatory effects of OIT continues to evolve, with new technologies such as single-cell transcriptional profiling and antibody epitope analysis allowing for more detailed study of T-cell and B-cell responses to OIT. In this review, we present evidence to illustrate what is currently known about the immunologic changes induced by OIT, explore potential mechanisms and emphasize knowledge gaps where future research is needed.