Potential mechanisms for the association between fall birth and food allergy

[Risk factors for cow's milk protein allergy in infants: a multicenter prospective nested case-control study]

OBJECTIVES

To explore the risk factors associated with cow's milk protein allergy (CMPA) in infants.

METHODS

This study was a multicenter prospective nested case-control study conducted in seven medical centers in Beijing, China. Infants aged 0-12 months were included, with 200 cases of CMPA infants and 799 control infants without CMPA. Univariate and multivariate logistic regression analyses were used to investigate the risk factors for the occurrence of CMPA.

RESULTS

Univariate logistic regression analysis showed that preterm birth, low birth weight, birth from the first pregnancy, firstborn, spring birth, summer birth, mixed/artificial feeding, and parental history of allergic diseases were associated with an increased risk of CMPA in infants (P<0.05). Multivariate logistic regression analysis revealed that firstborn (OR=1.89, 95%CI: 1.14-3.13), spring birth (OR=3.42, 95%CI: 1.70-6.58), summer birth (OR=2.29, 95%CI: 1.22-4.27), mixed/artificial feeding (OR=1.57, 95%CI: 1.10-2.26), parental history of allergies (OR=2.13, 95%CI: 1.51-3.02), and both parents having allergies (OR=3.15, 95%CI: 1.78-5.56) were risk factors for CMPA in infants (P<0.05).

CONCLUSIONS

Firstborn, spring birth, summer birth, mixed/artificial feeding, and a family history of allergies are associated with an increased risk of CMPA in infants.

The Natural History and Risk Factors for the Development of Food Allergies in Children and Adults

PURPOSE OF REVIEW

This narrative review explores food allergy prevalence and natural history stratified by life stages, especially in context of evolving knowledge over the last few decades.

RECENT FINDINGS

The prevalence of food allergy remains highest in early childhood with common food triggers being cow's milk, soy, hen's egg, wheat, peanut, tree nuts, sesame, fish, and shellfish. This correlates with certain risk factors especially pertinent in the postnatal period which appear to predispose an individual to developing a food allergy. Some allergies (such as milk and egg) were previously thought to be easily outgrown in early life; however, recent studies suggest increasing rates of persistence of these allergies into young adulthood; the reason behind this is unknown. Despite this, there is also evidence demonstrating that food allergies can be outgrown in adolescents and adults. An understanding of the paradigm shifts in the natural history of food allergy allows clinicians to provide updated, age-appropriate, and tailored advice for patients on the management and prognosis of food allergy.

The impact of temperature on the skin barrier and atopic dermatitis

Climate change is a global threat to public health and causes or worsens various diseases including atopic dermatitis (AD), allergic, infectious, cardiovascular diseases, physical injuries, and mental disorders. The incidence of allergy, such as AD, has increased over the past several decades, and environmental factors such as climate change have been implicated as a potential mechanism. A substantial amount of literature has been published on the impact of climate factors, including cold and hot temperatures, on the skin barrier and AD. Studies in several countries have found a greater incidence of AD in children born in the colder seasons of fall and winter. The effect of cold and warm temperatures on itch, skin flares, increased outpatient visits, skin barrier dysfunction, development of AD, and asthma exacerbations have been reported. Understanding mechanisms by which changes in temperature influence allergies is critical to the development of measures for the prevention and treatment of allergic disorders, such as AD and asthma. Low and high temperatures induce the production of proinflammatory cytokines and lipid mediators such as interleukin-1β, thymic stromal lymphopoietin, and prostaglandin E2, and cause itch and flares by activation of TRPVs such as TRPV1, TRPV3, and TRPV4. TRPV antagonists may attenuate temperature-mediated itch, skin barrier dysfunction, and exacerbation of AD.

Analysis of DNA methylation at birth and in childhood reveals changes associated with season of birth and latitude

BACKGROUND

Seasonal variations in environmental exposures at birth or during gestation are associated with numerous adult traits and health outcomes later in life. Whether DNA methylation (DNAm) plays a role in the molecular mechanisms underlying the associations between birth season and lifelong phenotypes remains unclear.

METHODS

We carried out epigenome-wide meta-analyses within the Pregnancy And Childhood Epigenetic Consortium to identify associations of DNAm with birth season, both at differentially methylated probes (DMPs) and regions (DMRs). Associations were examined at two time points: at birth (21 cohorts, N = 9358) and in children aged 1-11 years (12 cohorts, N = 3610). We conducted meta-analyses to assess the impact of latitude on birth season-specific associations at both time points.

RESULTS

We identified associations between birth season and DNAm (False Discovery Rate-adjusted p values < 0.05) at two CpGs at birth (winter-born) and four in the childhood (summer-born) analyses when compared to children born in autumn. Furthermore, we identified twenty-six differentially methylated regions (DMR) at birth (winter-born: 8, spring-born: 15, summer-born: 3) and thirty-two in childhood (winter-born: 12, spring and summer: 10 each) meta-analyses with few overlapping DMRs between the birth seasons or the two time points. The DMRs were associated with genes of known functions in tumorigenesis, psychiatric/neurological disorders, inflammation, or immunity, amongst others. Latitude-stratified meta-analyses [higher (≥ 50°N), lower (< 50°N, northern hemisphere only)] revealed differences in associations between birth season and DNAm by birth latitude. DMR analysis implicated genes with previously reported links to schizophrenia (LAX1), skin disorders (PSORS1C, LTB4R), and airway inflammation including asthma (LTB4R), present only at birth in the higher latitudes (≥ 50°N).

CONCLUSIONS

In this large epigenome-wide meta-analysis study, we provide evidence for (i) associations between DNAm and season of birth that are unique for the seasons of the year (temporal effect) and (ii) latitude-dependent variations in the seasonal associations (spatial effect). DNAm could play a role in the molecular mechanisms underlying the effect of birth season on adult health outcomes.

Associations between grass pollen exposures in utero and in early life with food allergy in 12-month-old infants

Birth during pollen seasons may influence food allergy risk but no study has assessed pollen exposure. Using the HealthNuts population-based cohort of 5276 infants, we assessed grass pollen exposures, in utero and up to the first 6 months of life, on hen's egg, sesame and peanut allergy outcomes at 12 months. Cumulative pollen exposure in the first 7 days of life increased risk of peanut sensitization aMOR (adjusted multinomial odds ratio) = 1.21 (95% CI: 1.01-1.44). Exposure between first 4-6 months of life increased risk of hen's egg aMOR = 1.02 (95% CI: 1.004-1.04) and sensitization to all foods aMOR = 1.02 (95% CI: 1.003-1.04). Grass pollen exposure was associated with food challenge diagnosed food allergy, but only among infants with a maternal history of food allergy. Exposure to grass pollen in the intrauterine period and infancy may be important but more studies are needed to replicate these findings.

Transient Receptor Potential Vanilloid 1 Plays a Major Role in Low Temperature-Mediated Skin Barrier Dysfunction

BACKGROUND

Children born in the fall and winter are at increased risk for developing atopic dermatitis (AD) and food allergy (FA). Since these seasons are associated with low temperature, we hypothesized that low temperature exposure may compromise keratinocyte differentiation and contribute to skin barrier dysfunction.

OBJECTIVE

To examine whether low temperature causes skin barrier dysfunction.

METHODS

Primary human epidermal keratinocytes (HEKs) were differentiated in 1.3mM CaCl₂ media and cultured at different temperatures. The cells were transfected with transient receptor potential cation channel subfamily V member 1 (TRPV1) or signal transducer and activator of transcription (STAT) 3 small-interfering RNA (siRNA) to examine the effects of these gene targets in HEKs exposed to low temperature. Gene expression of TRPV1, epidermal barrier proteins, and keratinocyte-derived cytokines were evaluated. Organotypic skin equivalents were generated using HEKs transfected with control or TRPV1 siRNA and grown at 25^oC or 37^oC. Transepidermal water loss (TEWL) and levels of epidermal barrier proteins were evaluated.

RESULTS

Filaggrin (FLG) and loricrin (LOR) expression, but not keratin (KRT)-1 and KRT-10 expression, was downregulated in HEKs incubated at 25^oC while TRPV1 silencing increased intracellular Ca²⁺ influx (keratinocyte differentiation signal) and enhanced the expression of epidermal differentiation proteins. Interleukin (IL)-1β and thymic stromal lymphopoietin (TSLP) induced by low temperature inhibited FLG expression in keratinocytes through the TRPV1/STAT3 pathway. Moreover, low temperature-mediated inhibition of FLG and LOR was recovered, and TEWL was decreased in organotypic skin transfected with TRPV1 siRNA.

CONCLUSION

TRPV1 is critical in low temperature-mediated skin barrier dysfunction. Low temperature exposure induced TSLP, an alarmin implicated in epicutaneous allergen sensitization.

CLINICAL IMPLICATIONS

Low temperature causes skin barrier dysfunction through TRPV1 and TSLP, which may explain the pathways involved in promoting allergic sensitization through the skin.

An Overview of Environmental Risk Factors for Food Allergy

IgE-mediated food allergy is an increasing public health concern in many regions around the world. Although genetics play a role in the development of food allergy, the reported increase has occurred largely within a single generation and therefore it is unlikely that this can be accounted for by changes in the human genome. Environmental factors must play a key role. While there is strong evidence to support the early introduction of allergenic solids to prevent food allergy, this is unlikely to be sufficient to prevent all food allergy. The purpose of this review is to summarize the evidence on risk factors for food allergy with a focus the outdoor physical environment. We discuss emerging evidence of mechanisms that could explain a role for vitamin D, air pollution, environmental greenness, and pollen exposure in the development of food allergy. We also describe the recent extension of the dual allergen exposure hypothesis to potentially include the respiratory epithelial barrier in addition to the skin. Few existing studies have examined the relationship between these environmental factors with objective measures of IgE-mediated food allergy and further research in this area is needed. Future research also needs to consider the complex interplay between multiple environmental factors.

Origin of Allergy From In Utero Exposures to the Postnatal Environment

As the incidence of atopic conditions continues to increase, emphasis has been placed on understanding the origin of allergy with hope that prevention measures can be achieved. The perinatal environment is important for this understanding, given that both the immune system and microbiome start forming prenatally. Maternal exposure can greatly impact on fetal health. Additionally, the dysfunctional epithelial barrier is influential in allowing allergens and irritants to penetrate the skin or mucosa, leading to the release of proinflammatory cytokines and mediators to drive type 2 tissue inflammation and the onset of allergy. There are numerous factors related to skin, airway, and gut epithelial barriers dysfunction, and genetic predispositions are also present. Comprehensive birth cohort studies and further mechanistic studies will be keys to understanding the origin of allergy.

A narrative review of vitamin D and food allergy in infants and children

OBJECTIVE

This article summarizes the research progress on the association of vitamin D and food allergy in infants and children.

BACKGROUND

In recent years, food allergy seriously has affected the quality of life of children and adults. Vitamin D is known to be involved in calcium and phosphorus metabolism, and recent research has demonstrated that vitamin D can also affect the immune regulation of food allergy.

METHODS

The present study summarizes the research progress on the association of vitamin D and food allergy in infants and children. We searched the PubMed database to identify studies on the association of vitamin D and food allergy published between January 2003 and August 2021.

CONCLUSIONS

Vitamin D in the body through a number of steps into the final formation of biological effects. The implications of postnatal vitamin D levels for food allergy may be even greater. Vitamin D can prevent the intestinal immune system from being exposed to allergens by maintaining the integrity of the mucosal barrier. Many clinical studies believe that vitamin D supplementation can improve infants' and children's food allergy, however, some show negative results or opposite results. A lot of laboratory studies have confirmed that vitamin D is involved in the immune regulation of food allergy. Evidence indicates there may be a nonlinear relationship between vitamin D and food allergy. Further researches need to be launched.

Prenatal and Perinatal Environmental Influences Shaping the Neonatal Immune System: A Focus on Asthma and Allergy Origins

It is suggested that programming of the immune system starts before birth and is shaped by environmental influences acting during critical windows of susceptibility for human development. Prenatal and perinatal exposure to physiological, biological, physical, or chemical factors can trigger permanent, irreversible changes to the developing immune system, which may be reflected in cord blood of neonates. The aim of this narrative review is to summarize the evidence on the role of the prenatal and perinatal environment, including season of birth, mode of delivery, exposure to common allergens, a farming environment, pet ownership, and exposure to tobacco smoking and pollutants, in shaping the immune cell populations and cytokines at birth in humans. We also discuss how reported disruptions in the immune system at birth might contribute to the development of asthma and related allergic manifestations later in life.

IgE-dependent sensitization to tropho- and aeroallergens with regard to age, sex and birth season of children and adolescents living in the north-eastern region of Poland

Introduction

A small number of studies concern trophoallergens and aeroallergens sensitization in the developmental age population in Poland. Only a few studies describe the role of selected factors determining the frequency and type of IgE-dependent sensitization in this population.

Aim

To assess the rate of sensitization to chosen tropho- and aeroallergens in the group of sensitized patients living in the north-eastern region of Poland with regard to age, sex and birth season.

Material and methods

Skin prick testing (SPT) with selected food allergens (trophoallergens) and airborne allergens was used to evaluate the sensitization process of patients recruited to this study between 1998 and 2012. A positive result of sensitization was defined when the patient had at least one positive skin prick test with the allergen studied. The skin prick tests were done after written consent had been obtained from the parents.

Results

Significant results were as follows: sensitization was more common in boys (41.9%) than in girls (35.7%); the highest percentage of sensitized patients was observed in the group of children aged 13–18 years (45.0%) as compared to the group of children up to 3 years old (the lowest 33.1%). The highest percentage of sensitized patients was observed among children born during winter (41.3%), the lowest among children born in autumn (36.8%).

Conclusions

The assessment of sensitization to chosen trophoallergens and airborne allergens should include the role of age, sex and birth season of the diagnosed patient.

Season of birth is associated with increased risk of atopic dermatitis in Japanese infants: a retrospective cohort study

Background

Several epidemiological studies have examined the possibility of a relationship between season of birth and atopic dermatitis (AD) and food allergy (FA), yet their results are contradictory. We investigated the association between season of birth and risk of AD and FA in Japanese infants.

Methods

Study subjects were 612 newborn infants born at a single obstetric/pediatric clinic without perinatal diseases. Season of birth was classified as spring (March-May), summer (June-August), autumn (September-November) or winter (December-February). AD was diagnosed according to the United Kingdom Working Party's criteria. FA was defined as present if there was a history of immediate allergic symptoms within 2 h after ingestion of a food. Specific IgE to the corresponding food was also assessed to support the diagnosis. We assessed the association between season of birth and risk of AD and FA using Cox proportional hazard models.

Results

We identified a total of 365 cases of AD occurring during 3659 person-months of follow-up. Compared with summer birth, autumn, winter, and spring birth were significantly positively associated with the risk of AD: adjusted HRs (95% CIs) were 2.67 (1.96-3.63), 1.42 (1.03-1.95), and 1.43 (1.04-1.98), respectively. We identified a total of 23 cases of physician-diagnosed FA occurring during 6815 person-months of follow-up.

Conclusions

Being born in the summer is associated with a lower risk of AD compared to other seasons of birth. The low incidence of FA in our cohort group made it difficult to establish a valid association between FA and season of birth as the statistical power was low.

Occurrence of pollen season at the end of the first trimester predicts clinical atopic diseases in the offspring: A Finnish population-based study

OBJECTIVE

To evaluate the association between potential exposure to different pollen concentrations at the 11th fetal week and subsequent clinical atopic diseases.

STUDY DESIGN AND SETTING

Parents of 1- to 4-year-old children (N = 3035) returned a questionnaire regarding physician-diagnosed atopic diseases. The children were born between 2001 and 2005 in the province of South Karelia, Finland. Results of allergy tests were collected from patient records in the area.

RESULTS

The prevalence of atopic diseases with sensitisation was higher in children whose 11th fetal week occurred during pollen rather than non-pollen season: atopic eczema 6.3% vs. 4.3% (adjusted odds ratio, aOR 1.58, 95% CI 1.10─2.28), food allergy 5.7% vs. 3.9% (1.63; 1.12─2.38), respiratory allergy or asthma 3.7% vs. 2.2% (2.03; 1.24─3.33) and any atopic diseases 7.4% vs. 5.5% (1.48; 1.07─2.05), respectively. Respectively, the prevalence was higher in the children exposed to high rather than low tree pollen concentrations (>1000 vs. <10 particles/m³) at the 11th fetal week: 12.1% vs. 4.4% (3.35; 1.89─5.95), 12.1% vs. 3.9% (3.77; 2.11─6.72), 4.7% vs. 2.5% (2.95; 1.21─7.20) and 14.0% vs. 5.7% (3.15; 1.86─5.35).

CONCLUSION

Coincidence of potential exposure to high tree pollen concentrations at the 11th fetal week is associated with subsequent clinical atopic diseases with sensitisation.

Food allergy is linked to season of birth, sun exposure, and vitamin D deficiency

The season of birth and ultraviolet B exposure have been related to the occurrence of food allergy. The levels of vitamin D produced from skin by ultraviolet B exposure might reflect this relationship. Vitamin D is known to induce antimicrobial peptides, protect intestinal flora, enhance the gut epithelial barrier, suppress mast cell activation and IgE synthesis from B cells, and increase the number of tolerogenic dendritic cells and IL-10-producing regulatory T cells. Vitamin D deficiency has been shown to exacerbate sensitization and allergic symptoms in a murine model of food allergy. However, in clinical situations, contradictory observations have been reported regarding the relationship between food allergy and vitamin D deficiency/supplementation. In this review, we have explored the links between food allergy and vitamin D levels. One explanation for the discrepant findings is confounding factors such as race, age, residency, skin color, and epigenetic changes that contribute to vitamin D levels. In addition, the season of birth influences the development of atopic dermatitis, which could lead to food sensitization. Finally, ultraviolet radiation could lead to regulatory T cell expansion and immunosuppression, irrespective of vitamin D status. Based on our current understanding, we believe that correction of vitamin D deficiency by supplementation, appropriate skin care, and sufficient ultraviolet radiation exposure could alter the prognosis of food allergy. To identify potential treatment strategies for food allergy, it is essential to gain a better understanding of the appropriate levels of vitamin D and ultraviolet radiation exposure.

How Different Parts of the World Provide New Insights Into Food Allergy

The prevalence and patterns of food allergy are highly variable in different parts of the world. Differences in food allergy epidemiology may be attributed to a complex interplay of genetic, epigenetic, and environmental factors, suggesting that mechanisms of food allergy may differ in various global populations. Genetic polymorphisms, migration, climate, and infant feeding practices all modulate food allergy risk, and possibly also the efficacy of interventions aimed at primary prevention of food allergy development. Approaches to diagnosis, treatment, and prevention of food allergy should thus be tailored carefully to each population's unique genetic and environmental make-up. Future research in the context of food allergy prevention should focus on elucidating factors determining differential responses between populations.

Primary Prevention of Food Allergy

PURPOSE OF REVIEW

This article summarises recent developments on the prevention of food allergy in terms of the 5 D's of the development of food allergy: dry skin, diet, dogs, dribble, and vitamin D.

RECENT FINDINGS

While several advances have improved our understanding of the development of food allergy, few preventive strategies have been implemented beyond changes in infant feeding guidelines. These now state that the introduction of allergenic solids such as peanuts should occur in the first year of life. Results from randomised controlled trials on other allergenic solids, vitamin D supplementation, BCG immunisation at birth and eczema prevention are eagerly anticipated in order to inform further preventative strategies.

Association of season of birth with DNA methylation and allergic disease

BACKGROUND

Season of birth influences allergy risk; however, the biological mechanisms underlying this observation are unclear. The environment affects DNA methylation, with potentially long-lasting effects on gene expression and disease. This study examined whether DNA methylation could underlie the association between season of birth and allergy.

METHODS

In a subset of 18-year-old participants from the Isle of Wight (IoW) birth cohort (n = 367), the risks of birth season on allergic outcomes were estimated. Whole blood epigenome-wide DNA methylation was measured, and season-associated CpGs detected using a training-and-testing-based technique. Validation method examined the 8-year-old Prevention and Incidence of Asthma and Mite Allergy (PIAMA) cohort. The relationships between DNA methylation, season of birth and allergy were examined. CpGs were analysed in IoW third-generation cohort newborns.

RESULTS

Autumn birth increased risk of eczema, relative to spring birth. Methylation at 92 CpGs showed association with season of birth in the epigenome-wide association study. In validation, significantly more CpGs had the same directionality than expected by chance, and four were statistically significant. Season-associated methylation was enriched among networks relating to development, the cell cycle and apoptosis. Twenty CpGs were nominally associated with allergic outcomes. Two CpGs were marginally on the causal pathway to allergy. Season-associated methylation was largely absent in newborns, suggesting it arises post-natally.

CONCLUSIONS

This study demonstrates that DNA methylation in adulthood is associated with season of birth, supporting the hypothesis that DNA methylation could mechanistically underlie the effect of season of birth on allergy, although other mechanisms are also likely to be involved.

Changes in Food-Specific IgE Over Time in the National Health and Nutrition Examination Survey (NHANES)

BACKGROUND

Food allergy prevalence appears to have recently risen, with larger increases among non-Hispanic blacks. However, it is unclear whether these trends represent shifts in recognition of food allergy or in sensitization.

OBJECTIVE

The objective of this study was to determine whether sensitization to common food allergens increased in US children from 1988-1994 to 2005-2006 and whether these trends differed by race and/or ethnicity.

METHODS

Food-specific immunoglobulin E (IgE; to peanut, milk, egg, and shrimp) was measured by ImmunoCAP in stored sera from subjects aged 6-19 in the National Health and Nutrition Examination Survey (NHANES) III (1988-1994) and was compared with NHANES 2005-2006. Sensitization to foods was defined as overall (IgE ≥ 0.35 kU/L), moderate level (IgE ≥ 2 kU/L), and high level (IgE ≥ commonly used 95% predictive values). Sensitization to individual and combined foods was compared between surveys, with analyses further stratified by race and/or ethnicity.

RESULTS

A total of 7896 subjects (NHANES III: n = 4995, NHANES 2005-2006: n = 2901) were included. In NHANES III, the prevalence of food sensitization was 24.3% (95% confidence interval [CI]: 22.1-26.5) compared with 21.6% (95% CI: 19.5-23.7) in NHANES 2005-2006. There were no significant changes in the prevalence of any level of milk, egg, or peanut sensitization, but shrimp sensitization at all levels decreased markedly; overall sensitization NHANES III: 11.2% (95% CI: 10.0-12.5) versus NHANES 2005-2006: 6.1% (95% CI: 4.5-7.7). There was a trend toward the increased prevalence of moderate- and high-level sensitization to the combination of milk, egg, and peanut among non-Hispanic blacks but not other groups.

CONCLUSIONS

In contrast to our expectations, sensitization to common food allergens did not increase between the late 1980s/early 1990s and the mid-2000s among US 6-19 year olds, and in fact decreased to shrimp.

The relationships among birth season, sunlight exposure during infancy, and allergic disease

Purpose

The recent increase in the prevalence of allergic diseases is hypothetically attributed to immune dysregulation in turn caused by a reduction in exposure to sunlight. We explored relationships between birth season, sunlight exposure, exercise duration, and an allergic disease.

Methods

We performed a questionnaire-based survey on allergic diseases among elementary school students. Birth time was categorized according to the season (summer and winter).

Results

The prevalence of atopic dermatitis (AD) "symptoms ever" was higher in the children born in winter than in those born in summer (adjusted odds ratio [aOR], 1.24; 95% confidence interval [CI], 1.03-1.49; P=0.024). Birth in winter was associated with an increase in the "symptoms in the past 12 months" prevalence of food allergy (FA) (aOR, 1.56; 95% CI, 1.09-2.24; P=0.015). The lifetime prevalence of allergic diseases except FA was higher in the children whose parents considered their sunlight exposure prior to 24 months of ageas inadequate than those who considered their exposure as adequate ("diagnosis ever" asthma: aOR, 1.4; 95% CI, 1.17-1.67; P<0.001; allergic rhinitis [AR]: aOR, 1.4; 95% CI, 1.17-1.67; P<0.001; AD: aOR, 1.26; 95% CI, 1.06-1.51; P=0.01). Neither recent sunlight exposure nor exercise duration was associated with the prevalence of an allergic disease.

Conclusion

Birth in winter may be associated with development of AD and FA. Inadequate sunlight exposure before the age of 24 months might possibly increase the risks of development of asthma, AR, and AD.

Sunlight, vitamin D and food allergy

PURPOSE OF REVIEW

The role of vitamin D in the development of food allergy is unclear. We summarize recent data on the epidemiologic link between sunlight (UVB) and food allergy, and evidence for and against a specific role for vitamin D status.

RECENT FINDINGS

Since 2007, most epidemiologic studies have supported low sunlight (as measured by season of birth and latitude) as a risk factor for food allergy. Investigators have also looked directly at vitamin D status (as measured by serum 25OHD level) and its potential role. Although conflicting, the vitamin D studies suggest a more complicated association than a linear dose response in all individuals, with some studies indicating different associations based on host characteristics (e.g. concominant eczema, genetic polymorphisms, country of birth). Most studies have not fully examined the myriad effects of sunlight but have instead focused on a single maternal, neonatal or childhood 25OHD level.

SUMMARY

Many studies have linked sunlight with the development of food allergy but whether this is directly related to vitamin D status or a myriad of other sunlight-derived, seasonal and/or geographic factors remains uncertain. More studies are needed to investigate the role of sunlight and vitamin D status in food allergy because of their potential for primary prevention and disease modification.

Spring season birth is associated with higher emergency department admission for acute allergic reactions

BACKGROUND

Acute allergic reactions are important causes of emergency department (ED) admission, imposing a significant clinical and organizational burden. Since the season of birth is linked with early exposure to allergens, this study was aimed to establish whether an association exists between season of birth and incidence and severity of acute allergic reactions in the ED.

METHODS

The electronic hospital database was searched to identify all consecutive adult patients who were admitted to the ED for acute allergic reactions (acute urticaria, acute angioedema, urticaria-angioedema and anaphylaxis) during a 1-year period.

RESULTS

The final study population consisted in 588 patients (328 women and 260 men; mean age 43 ± 18 years, range 16-96 years). Increased frequency of ED admission was observed for patients born in spring, whereas the lowest frequency was found for those born in autumn. Patients born in spring exhibited 1.19 and 1.12 higher risk of ED admission for acute allergic reactions compared to those born in autumn and in all other seasons, respectively. This difference remained significant in patients with allergic reaction attributable to drugs and in those with unknown triggers, whereas no pattern of seasonality was observed in patients with allergic reactions attributable to aliments, hymenoptera, chemicals or inhalants. Patients born in spring also exhibited 1.86 and 1.52 higher risk of being admitted to the ED for severe acute allergic reactions compared to those born in autumn and in all other seasons, respectively.

CONCLUSIONS

Patients born in spring appear particularly vulnerable to allergic reactions requiring ED visit.

Season of birth shapes neonatal immune function

BACKGROUND

Birth season has been reported to be a risk factor for several immune-mediated diseases. We hypothesized that this association is mediated by differential changes in neonatal immune phenotype and function with birth season.

OBJECTIVE

We sought to investigate the influence of season of birth on cord blood immune cell subsets and inflammatory mediators in neonatal airways.

METHODS

Cord blood was phenotyped for 26 different immune cell subsets, and at 1 month of age, 20 cytokines and chemokines were quantified in airway mucosal lining fluid. Multivariate partial least squares discriminant analyses were applied to determine whether certain immune profiles dominate by birth season, and correlations between individual cord blood immune cells and early airway immune mediators were defined.

RESULTS

We found a birth season-related fluctuation in neonatal immune cell subsets and in early-life airway mucosal immune function. The seasonal airway immune pattern was associated with the number of activated and regulatory T cells in cord blood whereas it was independent of concomitant presence of pathogenic airway microbes. Specifically, summer newborns presented with the lowest levels of all cell types and mediators; fall newborns displayed high levels of activated T cells and mucosal IL-12p70, TNF-α, IL-13, IL-10, and IL-2; and winter newborns had the highest levels of innate immune cells, IL-5, type 17-related immune mediators, and activated T cells.

CONCLUSION

Birth season fluctuations seem to affect neonatal immune development and result in differential potentiation of cord blood immune cells and early airway mucosal immune function.

The relationship between the season of birth and early-onset food allergies in children

BACKGROUND

This study examined the relationship between the season of birth (SoB) and other factors with the development of FA.

METHODS

A multicenter, cross-sectional pilot study recruited 1197 patients with FA. The main study recruited 440 incident cases (FA group) definitively diagnosed as FA at 0-1 year of age. In both studies, the frequency of autumn-winter births (AWBs) in FA patients was compared to the regional control population. In the main study, we analyzed the differences in the SoB and other factors between patients in the FA group and those in the non-FA group (n = 332) in allergy clinics.

RESULTS

The pilot study showed that the frequency of AWB (57.6%) in the FA patients was significantly higher than that of the regional control population (50.4%, OR, 1.34; p < 0.001). The main study also showed the dominance of AWB (62.7%) in the FA group in comparison with that in the regional control population (50.2%, OR, 1.70; p < 0.001). Preterm birth (OR, 0.43; p = 0.027) and the presence of two or more elder siblings (OR, 0.27; p = 0.012) were significantly associated with a lower frequency of FA than those of non-FA. AWB (RR, 1.21; p = 0.020) and preterm birth (RR, 0.55; p = 0.017) were significantly associated with a number of trigger foods. The SoB effect was observed in FA patients irrespective of the presence of infantile eczema.

CONCLUSIONS

AWB was predominant in the patients with newly diagnosed food allergies.

Sun exposure inversely related to food sensitization during infancy

BACKGROUND

Autumn and winter birth (AWB) has been reported to be a risk factor for the development of food allergies. However, the association between seasonal factors and allergic sensitization during early infancy remains unclear.

METHODS

We collected data from 732 patients regarding the total and specific immunoglobulin E (tIgE, sIgE) levels in infants younger than 6 months old from November 2001 to October 2012 from the institutional clinical database system. We then analyzed the relationship between the birth month and the value of each parameter. Furthermore, we identified any correlations between the number of sensitized patients and the monthly climatological parameters.

RESULTS

The number of tIgE samples obtained from AWB patients (n = 482) was 2.1 times higher than that from patients born in the spring and summer (SSB, n = 225). The number of sIgE samples to egg white, cow's milk, and wheat, the sensitized ratio and the median sIgE titer were also all higher in AWB. The number of sensitized AWB patients to these allergens was 2.75, 3.05, and 3.97 times higher, respectively. A periodic change in the number of sensitized patients was observed annually (highest in October-November and lowest in May). Among the climatological parameters examined, the average solar radiation during the 3-month period after birth showed the strongest negative correlation with the number of sensitized patients (egg white: r = -0.976, cow's milk: r = -0.969, wheat: r = -0.975).

CONCLUSIONS

The amount of solar radiation immediately after birth had a strong negative correlation with allergen sensitization before 6 months of age.

Food allergen sensitization in young children with typical signs and symptoms of immediate-type food allergies: a comparison between monosensitized and polysensitized children

PURPOSE

The clinical interpretation of children sensitized to allergens is challenging, particularly in children with food allergies. We aimed to examine clinical differences between children with monosensitization and those with polysensitization to common food allergens and to determine risk factors for polysensitization in young children <10 years of age with immediate-type food allergies.

METHODS

The study included children <10 years of age with signs and symptoms indicative of immediate-type food allergies. Serum total IgE level was measured, and ImmunoCAP analysis for food allergens was performed.

RESULTS

The mean age of the study subjects was 1.6±1.6 years (75 boys and 51 girls). Thirty-eight children (30.2%) were monosensitized and 88 children (69.8%) were polysensitized. Multivariate logistic regression analysis showed that the development of polysensitization to common food allergens was positively associated with a parental history of allergic rhinitis (adjusted odds ratio [aOR], 6.28; 95% confidence interval [CI], 1.78-22.13; P=0.004), season of birth (summer/fall) (aOR, 3.10; 95% CI, 1.10-8.79; P=0.033), and exclusive breastfeeding in the first 6 months of age (aOR, 3.51; 95% CI, 1.20-10.25; P=0.022).

CONCLUSION

We found significant clinical differences between children with monosensitization and those with polysensitization to common food allergens and identified risk factors for the development of polysensitization in young children with immediate-type food allergies. Clinicians should consider these clinical risk factors when evaluating, counseling, treating, and monitoring young children with food allergies.

Food allergy: epidemiology and natural history

The prevalence of food allergy is rising for unclear reasons, with prevalence estimates in the developed world approaching 10%. Knowledge regarding the natural course of food allergies is important because it can aid the clinician in diagnosing food allergies and in determining when to consider evaluation for food allergy resolution. Many food allergies with onset in early childhood are outgrown later in childhood, although a minority of food allergy persists into adolescence and even adulthood. More research is needed to improve food allergy diagnosis, treatment, and prevention.

The link between serum vitamin D level, sensitization to food allergens, and the severity of atopic dermatitis in infancy

OBJECTIVE

To investigate the association between serum vitamin D levels, sensitization to food allergens, and the severity of atopic dermatitis in infants.

STUDY DESIGN

We investigated serum 25-hydroxyvitamin D (25[OH]D) and specific immunoglobulin E levels to common or suspected food allergens in 226 infants with atopic dermatitis or food allergy. The severity of atopic dermatitis by the Scoring Atopic Dermatitis index and amount of vitamin D intake was measured in subcohort children. Sensitization to food allergen was categorized by the number (non-, mono-, and poly-) of sensitized allergens and the degree (undetected-, low-, and high-level) of sensitization.

RESULTS

Significant differences in 25(OH)D levels were found between groups on number (P = .006) and degree (P = .005) of food sensitization. The polysensitization group had significantly lower levels of 25(OH)D than the nonsensitization (P = .001) and monosensitization (P = .023) group. High-level sensitization group had significantly lower 25(OH)D levels compared with undetected (P = .005) and low-level (P = .009) sensitization group. Vitamin D deficiency increased the risk of sensitization to food allergens (OR 5.0; 95% CI 1.8-14.1), especially to milk (OR 10.4; 95% CI 3.3-32.7) and wheat (OR 4.2; 95% CI 1.1-15.8). In addition, the Scoring Atopic Dermatitis index was independently related to 25(OH)D levels after adjusting for the level of sensitization (adjusted R(2) = 0.112, P = .031).

CONCLUSIONS

Our results suggest that vitamin D deficiency increases the risk of sensitization to food allergens and that atopic dermatitis may be more severe in infants with vitamin D deficiency.

Determinants of sensitization to allergen in infants and young children

Atopic sensitization is a complex phenomenon that changes dynamically with age throughout childhood; its prevalence increases with age in young children. Additionally, with increasing age, the prevalence of sensitization to inhalant allergens and the prevalence of polysensitization to allergens increase. It is also well established that the development of atopic sensitization is the result of a complex interplay of genetic and environmental factors. However, there is considerable heterogeneity in the literature in terms of the effect of different environmental exposures in young children on the subsequent risk of atopic sensitization and allergic diseases. Previous studies on the relationship, in early life, between pet ownership, sex, exposure to secondhand smoke, exposure to traffic-related air pollution components, and atopic sensitization have yielded different results. Recent studies have highlighted the importance of gene-environment interactions, especially during early childhood, on the risk of subsequent atopic sensitization and allergic diseases. Therefore, pediatricians should consider the genetic and environmental determinants of atopic sensitization in infants and young children when diagnosing and treating patients with allergic diseases. Determining ways in which early exposure to these risk factors in young children may be reduced could be beneficial in preventing the likelihood of developing atopic sensitization.

Temporal trends and racial/ethnic disparity in self-reported pediatric food allergy in the United States

BACKGROUND

The prevalence of food allergy is thought to be increasing, but data from the United States have not been systematically synthesized.

OBJECTIVE

To summarize the data on prevalence of food allergy in the US pediatric population and to estimate the effects of time, race/ethnicity, and method of assessing food allergy on the estimated prevalence.

METHODS

Embase, MEDLINE, bibliographies of identified reports, and data from publically available data sets were searched. Studies were limited to those in English with data from the general pediatric US population. Study synthesis was performed by meta-analysis and meta-regression to estimate the effect of study- and participant-level covariates. Meta-regression was limited to nationally representative surveys conducted by the Centers for Disease Control and Prevention.

RESULTS

A total of 10,090 publications were identified, from which 27 different survey administrations, representing 452,237 children, were identified, covering the period of 1988 to 2011. Because of heterogeneity among surveys in the estimated food allergy prevalence, a summary estimate of food allergy prevalence was not possible. Meta-regression was performed using 20 of these surveys. Temporal trends were pronounced, with an estimated increased prevalence of self-reported food allergy of 1.2 percentage points per decade (95% confidence interval [CI], 0.7-1.6). The increase per decade varied by race/ethnicity: 2.1% among non-Hispanic blacks (95% CI, 1.5%-2.7%), 1.2% among Hispanics (95% CI, 0.7%-1.7%), and 1.0% among non-Hispanic whites (95% CI, 0.4%-1.6%).

CONCLUSION

Self-report of food allergy among US children has sharply increased in the past 2 decades. The increase has been greatest among non-Hispanic black children, a disparity that needs to be investigated.

Mechanisms and potential therapeutic targets in allergic inflammation: recent insights

Deeper insight into pathogenetic pathways and into the biological effects of immunomodulatory agents will help to optimize or adopt therapeutic strategies for atopic disorders. In this article, we highlight selected findings of potential therapeutic relevance that emerged from recent mechanistic studies with focus on molecular and cellular aspects of allergic inflammation. Furthermore, the often complex mechanisms of action of pleiotropic immunomodulatory agents, such as glucocorticoids, vitamin D, or intravenous immunoglobulin (IVIG), are discussed, as their dissection might reveal targets for novel therapeutics or lead to a more rational use of these compounds. Besides reporting novel evidence, this article points to areas of current debate or uncertainty and aims at stimulating scientific discussion and experimental work.

Food allergy diagnosis and therapy: where are we now?

Food allergy is a growing worldwide epidemic that adversely effects up to 10% of the population. Causes and risk factors remain unclear and diagnostic methods are imprecise. There is currently no accepted treatment for food allergy. Therefore, there is an imminent need for greater understanding of food allergies, revised diagnostics and development of safe, effective therapies. Oral immunotherapy provides a particularly promising avenue, but is still highly experimental and not ready for clinical use.

Progress in understanding the epigenetic basis for immune development, immune function, and the rising incidence of allergic disease

The profile of allergic disease worldwide continues to change as the number of severe IgE-mediated allergies increases. This phenomenon is thought to reflect the outcome of combined genetic/environmental/developmental/stochastic effects on immune development, but understanding this remains a challenge. Epigenetic disruption at key immune genes during development has been proposed as a potential explanation for how environmental exposures may alter immune cell development and function. This represents an emerging area of research with the potential to yield new understanding of how disease risk is modified. Here, we examine recent developments in this field that are defining new epigenetic paradigms of allergic disease.

Maternal and newborn vitamin D status and its impact on food allergy development in the German LINA cohort study

BACKGROUND

Vitamin D levels are known to be associated with atopic disease development; however, existing data are controversial. The aim of this study was to investigate whether corresponding maternal and cord blood vitamin D levels are associated with atopic outcomes in early infancy.

METHODS

Within the LINA cohort study (Lifestyle and environmental factors and their Influence on Newborns Allergy risk), 25(OH)D was measured in blood samples of 378 mother-child pairs during pregnancy and at birth. Information about children's atopic manifestations during the first 2 years of life was obtained from questionnaires filled out by the parents during pregnancy and annually thereafter. Cord blood regulatory T cells (Treg) were detected by methylation-specific PCR using a Treg-specific demethylated region in the FOXP3 gene.

RESULTS

The median maternal 25(OH)D(3) level was 22.19 ng/ml (IQR 14.40-31.19 ng/ml); the median cord blood 25(OH)D(3) 10.95 ng/ml (6.99-17.39 ng/ml). A high correlation was seen between maternal and cord blood 25(OH)D(3) levels, both showing a seasonal distribution. Maternal and cord blood 25(OH)D(3) was positively associated with children's risk for food allergy within the first 2 years. Further, higher maternal 25(OH)D(3) resulted in a higher risk for sensitization against food allergens at the age of two. Cord blood 25(OH)D(3) levels were negatively correlated with regulatory T cell numbers.

CONCLUSION

Our study demonstrates that high vitamin D levels in pregnancy and at birth may contribute to a higher risk for food allergy and therefore argues against vitamin D supplement to protect against allergy.

Effect of eczema on the association between season of birth and food allergy in Japanese children

BACKGROUND

Food allergy (FA) in childhood has been shown to be more prevalent in those born in autumn and winter. The mechanisms of this season-of-birth effect remain unclear, although shortage of vitamin D during infancy has been considered one possible mechanism. The purpose of this study was to investigate the effect of eczema on the season-of-birth effect on FA in infancy.

METHODS

A questionnaire survey on the prevalence of allergic diseases was completed by the parents of 14 669 Japanese schoolchildren, aged 7-15 years, in Kyoto City, Japan. Logistic regression models were constructed to compare the prevalence of FA in infancy according to season of birth.

RESULTS

Those born in autumn and winter had a significantly higher prevalence of FA in infancy compared to those born in spring and summer in a multivariate model (4.8% vs 3.6%, P = 0.001). The difference, however, was no longer significant when eczema before 6 months was included as either an additional or only confounding factor. The difference among those with and without eczema before 6 months was further analyzed, and it was found that, in both groups, there was no difference between those born in spring and summer and those born in autumn and winter.

CONCLUSIONS

The season-of-birth effect on FA in infancy was significantly affected by the existence of eczema before 6 months in Japanese children. Eczema before 6 months may be the factor directly related to the season-of-birth effect on FA in infancy.