Genetic, environmental and lifestyle factors influence the risk for food sensitization and food allergies during the first thousand days of life, according to a literature review published in Annals of Allergy, Asthma & Immunology.
Erin C. Davis, PhD, postdoctoral fellow in the department of pediatrics’ division of allergy and immunology at the University of Rochester School of Medicine and Dentistry and the Center for Food Allergy at Golisano Children’s Hospital, University of Rochester Medical Center, in Rochester, N.Y., based their findings on a PubMed search of articles in English on food allergy (FA) and food sensitization (FS), prioritizing studies published after 2015.
The review explored the genetic risks for food allergy, links between atopic dermatitis (AD) and food allergy, dietary allergen exposures in early life, maternal antigen consumption during pregnancy and lactation, breastfeeding and formula feeding, introduction to solid foods, lifestyle and environmental exposures, the gut microbiome and metabolome in food allergy and potential early immune biomarkers of food allergy.
Genetic risks for food allergy include the number of parents or siblings with a history of allergic disease, although the researchers caution that some of this association may be due to the family’s practice of prolonged avoidance or late introduction of the allergen.
Specifically, researchers have found connections between the major histocompatibility complex genes, which encode the human leukocyte antigen complex, and FA development including sensitization to peanut, cow’s milk and egg.
The review also revealed that approximately one-third of children with AD are susceptible immediately-type IgE-mediated FA. One hypothesis is that patients with AD have an impaired skin barrier, which allows them to epicutaneously sensitize to foods before they are eaten.
The researchers noted that infants could be exposed to allergens at an early age. They also suggested that the mechanisms that cause tolerance and sensitization may differ depending on how that exposure occurred.
The researchers suggested that infants may be exposed in utero to allergens or through infant formula or human milk before they are able to eat solid foods. It is possible that allergens may be exposed to household or environmental allergens.
The researchers did not find any evidence linking maternal allergen intake to infant FA risk. However, major food allergens were detected in human milk and amniotic fluid. The American Academy of Pediatrics recommends that mothers not eat certain foods to prevent atopic disease.
Researchers said that studies that evaluated the protective effects of breastfeeding against FA were mixed. Human milk contains immunomodulatory ingredients that help to shape the immune system and early life microbiome. However, the risk of getting sick can vary between women.
Researchers cited the Learning Early About Peanut trial which showed how peanut intake could help prevent peanut allergy. The Enquiring About Tolerance Study also found that children aged between 1 and 3 years had a 67% lower chance of developing FA from early introduction.
Researchers also found that increasing rates of FA or FS may be due to Westernization, which reduces industrialized exposures.
Higher incidences of AD or hay fever are associated with larger families. Vaginal delivery and exposure to pets are also associated with lower risk of allergic diseases. Protective lifestyles such as farming can also be beneficial.
Researchers believe that early exposures to diverse microorganisms could help the immune system mount tolerogenic reactions to food or environmental allergens.
The association between allergic disease prevalence and industrialization is also mediated by the gut microbiome. The researchers believe that FA may be associated with FS development and less mature microbiomes. However there are limited studies.
The researchers also found studies that showed associations between FA and a differential infant immune profile. Researchers stated that the potential loss of immune cell populations or hyper-responsive profiles could increase risk for abnormal responses, including sensitization.
Multiple factors are involved in disease pathogenesis. These include genetics as well maternal and infant allergens exposures, human milk composition and other environmental variables. Tolerance and sensitization depend on the route of exposures and potential genetic risk.
The researchers also requested additional observational studies and clinical trial that covered the entire life span of FS and FA, so that novel biomarkers and risk factors could be identified for predicting susceptibility to FS and FA.
