Allergies and Maternal Diet

Dive Deeper
What causes allergies?

An allergy is an adverse immune response to a foreign substance that doesn’t cause a reaction in most people. The immune system produces a special antibody, called immunoglobulin E (IgE) when it encounters this foreign substance. Immunologists still debate about the exact cause of allergies, although many theorize that allergies are caused by an imbalance between an inflammatory immune reaction and the anti-inflammatory, IgE-producing immune reaction.1

Children usually experience the allergy symptoms the very first time that they eat a food. Food-related allergies are the leading cause of emergency room visits in which the young child cannot breathe. The prevalence of allergies keeps increasing. From 1997 to 2008, the prevalence of children with peanut allergies jumped from 0.2% to 1.1%.2 In 2017, 2.2% of children had a peanut allergy.3

Researchers sometimes disagree, but in general, a child is less likely to be allergic to food that his mother consumed while she was pregnant.
In general, a child is less likely to be allergic to food that his mother consumed while she was pregnant. (Image Credit: Science Source)

Researchers sometimes disagree, but in general, a child is less likely to be allergic to food that his mother consumed while she was pregnant. For example, when pregnant women drank a lot of milk, their children were less likely to have milk allergies,4 and when pregnant mothers ate 5 servings of peanuts each week, their children were less likely to have peanut allergies.5 When children with a high risk of peanut allergy were introduced to peanuts between 4 and 10 months old, they were less likely to develop a peanut allergy later in childhood.6 The maximum anti-allergy benefits seem to come from exposure to the mother’s diet in the first trimester of pregnancy.7 Although some studies do not find an association between a mother’s diet and her children’s future allergies, the most sensitive studies, or ones that examined the most people show that food exposure may help prevent severe allergies. Most studies also conclude that adequate nutrition helps protect kids against allergies.  Ensuring that pregnant mothers have enough vitamin D also reduces the risk of allergies in their children.8

What about allergies to things other than food?

Researchers have found that mothers with allergies tend to have children who develop allergies, although the children respond to different allergens than their mothers,9 suggesting a genetic component, or an immune interaction in utero. A number of environmental factors also seem to increase the risk of allergies in children, including in utero stress, smoking, and poor nutrition.10

The month that a baby is born can influence his risk for pollen-induced allergies. When a mother gets exposed to lots of pollen, the fetus produces more immunoglobulin E (IgE), an immune marker used to predict the development of allergic diseases, as measured by level in the umbilical cord blood. If a baby is born during the high-pollen season, then that baby is born with more IgE in his blood and is more likely to develop allergies than normal. However, if the baby stays in the womb for an entire allergy season, then that baby is less likely to develop allergies than normal.11

Interestingly, when pregnant mothers receive allergy shots, their children tend to have a lower risk of developing the same allergy for the first eight years of their life.12 Also of note, when babies are born vaginally rather than by cesarean delivery, they are less likely to develop allergies in childhood. Researchers have theorized that this is because babies born vaginally get exposed to unique microbes in the vaginal canal,13 although this has yet to be proven.