The Effect of Breastmilk on Food Allergy Development
Research is unclear if exposure to food allergens in breastmilk is protective or could prime allergic sensitization to food allergens.
The World Health Organization (WHO) characterizes breastfeeding as "one of the most effective ways to ensure child health and survival". Recommendations support exclusive breastfeeding for 6 months, after which complementary foods may be introduced while breastfeeding continues for up to 2 years of age or longer.
Breastmilk provides children with complete nutrition, and can be protective against gastrointestinal infections as well as a range of diseases and adverse health conditions later in life.
The most recent American Academy of Pediatrics guidance shows that breastfeeding is protective against asthma, wheezing, and ezcema. Research demonstrates that exclusive breastfeeding for 3 to 4 months decreases the incidence of eczema in the first 2 years of life, exclusive breastfeeding for at least 3 months protects against wheezing early in life, and a longer duration of breastfeeding protects against asthma after 5 years of age.
Current research does not support the need for maternal dietary restrictions while breastfeeding, unless breastfed infants show direct symptoms due to maternal intake of food allergens. However, there is a lack of research regarding the relationship between breastfeeding on food allergy outcomes and the role of breastfeeding in preventing or contributing to food allergies.
In immunology, allergic sensitization refers to the induction of an immune response when exposed to an allergen. It is currently not known whether breastfeeding could play a role in allergic sensitization to food allergens in breastfed children.
There are challenges in making a determination regarding the influence of breastfeeding on food allergy outcomes. Two such challenges are that breastfeeding exposure can't be randomized, and breastmilk composition varies significantly based on multiple factors. Composition varies depending on the nursing stage, time of day of a feeding, a mother's diet and health status, and environmental factors.
One study found that maternal peanut consumption while breastfeeding and early introduction of peanut-containing food were associated with reduced risk of peanut sensitization when compared to maternal peanut consumption while breastfeeding with delayed introducion of peanuts, and maternal avoidance of peanuts with introduction of peanuts by 12 months.
One review on the subject notes that "some breastfed children are described to be sensitized to foods before being exposed to solid foods, and this exposure may have occurred through breastmilk." Food allergens have been detected in bresatmilk, and certain allergens can transfer through breastmilk, but it is unclear if and how they might affect sensitization in the infant.
Further studies are needed to understand the role of breastfeeding in sensitization and protection against food allergies in infants.
Resources & Information on Breastfeeding and Food Allergies
American Academy of Pediatrics, Clinical Report
World Health Organization, Breastfeeding Fact Sheet