Dietary exposures and allergy prevention in high-risk infants

The Relationship Between Dietary Patterns and the Epidemiology of Food Allergy

Food allergies are increasing globally, particularly in Asia; however, the etiologies of allergic diseases remain poorly understood despite comprehensive studies conducted across a variety of populations. Epidemiological research demonstrates that food allergy is more prevalent in Westernized or urbanized societies than in rural or developing ones. As such, comparing the distribution and patterns of food allergies as well as the environmental exposures between regions may provide insight into potential causal and protective factors of food allergy. Diet is an important exposome that has been shown to modulate the immune system both directly and indirectly via pathways involving the microbiota. Changes in dietary patterns, especially the shift to a Westernized diet with reduced dietary fiber and an abundance of processed foods, impact the gut and skin epithelial barrier and contribute to the development of chronic inflammatory diseases, such as food allergy. Although dietary intervention is believed to have tremendous potential as a strategy to promote immunological health, it is essential to recognize that diet is only one of many factors that have changed in urbanized societies. Other factors, such as pollution, microplastics, the use of medications like antibiotics, and exposure to biodiversity and animals, may also play significant roles, and further research is needed to determine which exposures are most critical for the development of food allergies.

Awareness and Application of United States Food Allergy Prevention Guidelines Among Pediatricians and Other Clinicians

OBJECTIVE

To characterize the awareness of, adherence to, and barriers to the 2017 National Institute of Allergy and Infectious Diseases (NIAID) peanut allergy prevention guidelines among the pediatrics health care workforce.

STUDY DESIGN

Pediatricians, family physicians, advanced practice providers (APPs), and dermatologists who provide care for infants were solicited for a population-based online survey, administered from June 6, 2022, through July 3, 2022. The survey collected information about NIAID guideline awareness, implementation, and barriers as well as concerns related to the guidelines.

RESULTS

A total of 250 pediatricians, 250 family physicians, 504 APPs, and 253 dermatologists met inclusion criteria. Self-reported guideline awareness was significantly higher for pediatricians (76%) compared with dermatologists (58%), family physicians (52%), and APPs (45%) (P < .05). Among participants who were aware of the guidelines, most reported using part or all of the guidelines in their clinical practices. Reported practice patterns for peanut introduction in 6-month-old infants were variable and did not always align with guidelines, particularly for infants with mild-to-moderate atopic dermatitis.

CONCLUSIONS

Although pediatricians have the highest self-reported level of NIAID guideline awareness, awareness was suboptimal irrespective of provider type. Education for all pediatric clinicians is urgently needed to promote evidence-based peanut allergy prevention practices.

Prevalence and Determinants of Food Allergy in the Era of Early Allergen Introduction: The EarlyNuts Population-Based Study

BACKGROUND

Infant feeding guidelines in Australia changed in 2016 to recommend introducing common allergy-causing foods by age 1 year to prevent food allergy. Although most Australian infants now eat peanut and egg by age 6 months, some still develop food allergy despite the early introduction of allergens.

OBJECTIVES

To describe the prevalence of food allergy in a cohort recruited after introducing the nationwide allergy prevention recommendations; identify characteristics of infants who developed allergy despite early introduction of allergens; and estimate the causal effect of modifiable exposures on food allergy prevalence and whether this differed between infants who were introduced to allergens before or after age 6 months.

METHODS

We recruited a population-based sample of 12-month-old infants in Melbourne, Australia. Infants had skin prick tests to four foods and parents completed questionnaires. Infants with evidence of sensitization were offered oral food challenges. Prevalence estimates were adjusted using inverse probability weighting.

RESULTS

In a cohort of infants (n = 1,420) in which nearly all infants had been introduced to common allergens such as egg, milk, and peanut by age 1 year, the prevalence of food allergy remained high at 11.3% (95% CI, 9.6-13.4). Infants who developed food allergy despite introduction of the allergen by age 6 months were more likely to have Asian-born parents. Early-onset moderate or severe eczema was associated with an increased odds of food allergy irrespective of whether allergens were introduced before or after age 6 months. Among infants who were introduced to peanut at age 6 months or earlier, antibiotic use by age 6 months was associated with an increased odds of peanut allergy (adjusted odds ratio = 6.03; 95% CI, 1.15-31.60).

CONCLUSIONS

In a cohort in which early allergen introduction was common, the prevalence of food allergy remained high. Infants who developed food allergy despite introduction of the respective allergen by age 6 months were more likely to have had Asian parents and early-onset eczema. New interventions are needed for infants with a phenotype of food allergy that is not amenable to early allergen introduction.

Environmental Interventions for Preventing Atopic Diseases

PURPOSE OF REVIEW

In this review, we detail the exposome (consisting of environmental factors such as diet, microbial colonization, allergens, pollutants, and stressors), mechanistic and clinical research supporting its influence on atopic disease, and potentiation from climate change. We highlight contemporary environmental interventions and available evidence substantiating their roles in atopic disease prevention, from observational cohorts to randomized controlled trials, when available.

RECENT FINDINGS

Early introduction to allergenic foods is an effective primary prevention strategy to reduce food allergy. Diverse dietary intake also appears to be a promising strategy for allergic disease prevention, but additional study is necessary. Air pollution and tobacco smoke are highly associated with allergic disease, among other medical comorbidities, paving the way for campaigns and legislation to reduce these exposures. There is no clear evidence that oral vitamin D supplementation, prebiotic or probiotic supplementation, daily emollient application, and antiviral prophylaxis are effective in preventing atopic disease, but these interventions require further study. While some environmental interventions have a well-defined role in the prevention of atopic disease, additional study of many remaining interventions is necessary to enhance our understanding of their role in disease prevention. Alignment of research findings from randomized controlled trials with public policy is essential to develop meaningful public health outcomes and prevent allergic disease on the population level.

Nurturing Infants to Prevent Atopic Dermatitis and Food Allergies: A Longitudinal Study

BACKGROUND

Atopic dermatitis (AD) at a young age often precedes the development of food allergies. Although AD affects millions of infants worldwide, prenatal and postnatal risk factors, and their association with the development of food allergies later on, are not fully elucidated. This study seeks to investigate AD epidemiology in infancy and its risk factors, examining early-life factors (both prenatal and postnatal) that could contribute to the later development of food allergies.

METHODS

Between January 2019 and December 2019, 501 infants were included in this prospective cohort study. Longitudinal data collection was performed through maternal interviews, the first one conducted within three days after the delivery and the second within 24 to 36 months after the delivery, encompassing variables such as demographics, family history of atopy, maternal smoking, antibiotic use during pregnancy, the mode of delivery, breastfeeding history, food practices, and greenness exposure within 3 days from delivery, while they were still in the hospital.

RESULTS

Maternal smoking during pregnancy (p = 0.001) and an older sibling atopy history (p = 0.03) was significantly linked to AD incidence. Cesarean section delivery (p = 0.04) was associated with a higher risk of food allergies in infants with AD. Having a garden at home correlated with a higher likelihood of AD (p = 0.01), and food elimination without medical guidance (p = 0.02) due to AD correlated with an elevated risk of food allergies.

CONCLUSIONS

Encouraging timely allergenic food introduction while promoting dietary diversity, rich in plant-based foods, maternal smoking cessation, and professional dietary guidance may help minimize AD and food allergy risk. Future studies should address the role of greenness in the development of AD and food allergies.

Updates in Food Allergy Prevention in Children

Although significant evidence exists that feeding early has a role in the prevention of food allergy, this intervention in isolation may not be sufficient. Recent evidence highlights that early introduction of peanut specifically has had no significant impact on the populational prevalence of peanut allergy. Other factors that may contribute to food allergy prevention include regularity of ingestion once an allergen is introduced and consideration to the form in which the allergen is introduced (such as baked versus cooked egg). There are also many practicalities to early feeding and some discrepant viewpoints on these practicalities, which has led to poor implementation of early feeding strategies. In general, preemptive screening before food introduction is not recommended by most international allergy societies. Although there is little guidance to inform early introduction of allergens other than milk, egg, and peanut, the mechanism of sensitization is thought to be similar and there is no harm to early introduction. In terms of frequency and duration of feeding, there is little evidence to inform any concrete recommendations.

Primary Prevention of Allergy - Is It Feasible?

The allergy epidemic has been attributed to environmental influences related to urbanization and the modern lifestyle. In this regard, various theories exploring the role of microbes (hygiene, old friends, microbiota, and biodiversity hypotheses), and the epithelial barrier (epithelial, dual allergen exposure and vitamin D hypotheses) have been proposed. These hypotheses have guided clinical studies that led to the formulation of intervention strategies during the proposed window of opportunity dubbed as the "first thousand days." The most significant intervention is a paradigm shift from allergen avoidance to early introduction of allergenic foods, particularly egg and peanut, around 6 months of age for the prevention of food allergy. This recommendation has been adopted globally and included in allergy prevention guidelines. Other strategies with less robust clinical evidence include: encouraging a healthy balanced diet, rich in fish, during pregnancy; continuing allergenic food intake during pregnancy and lactation; vitamin D supplementation in pregnant women with asthma; discouraging social indications for caesarean section delivery; judicious use of antibiotics in early childhood; daily emollient use from birth in high risk babies; and avoiding cow's milk formula use in the first week of life. However, if early supplementation with cow's milk formula is required, continuing at least 10 mL of formula daily until age 2 months may be considered. Translating these strategies to public health and clinical practice is still a work in progress. Long-term population studies are crucial to assess the feasibility of these measures on allergy prevention.

Atopic dermatitis and food allergy: To Test or not to test

One of the most challenging clinical scenarios in the field of allergy and immunology is the patient with uncontrolled atopic dermatitis (AD) and potential food allergy. These two diagnoses often coexist, but false-positive testing to foods is also prevalent. Physicians and other health care professionals may be concerned that not testing enough foods could lead to worsened AD severity or future systemic food reactions. However, testing too many foods can cause unnecessary food avoidance with varied subsequent consequences. Adding to this dilemma, patients and families with AD often request food allergy testing or present with test results in need of interpretation. The best path forward for these patients is nuanced, but evidenced-based medicine indicates that "less is more" when it comes to food allergy testing in patients with AD. This review explores when food testing is indicated based on the latest research and guidelines in food allergy and AD.

Prevention of food allergy in infancy: the role of maternal interventions and exposures during pregnancy and lactation

There is increased focus on the role of maternal interventions in the prevention of food allergy in infancy. There is no role for maternal dietary modifications during pregnancy or lactation, such as allergen avoidance, as a means of infant allergy prevention. Although exclusive breastfeeding is the recommended infant nutrition source globally, the effect of breastfeeding on infant allergy prevention remains unclear. There is emerging evidence that irregular cow's milk exposure (ie, infrequent formula supplementation) might increase the risk of cow's milk allergy. Although further studies are required, there is also emerging evidence that maternal peanut ingestion during breastfeeding along with early peanut introduction in infancy might have a preventive role. The effect of maternal dietary supplementation with vitamin D, omega-3, and prebiotics or probiotics remains unclear.