Do Food Allergies Begin Before Birth?
Food allergies are on the rise. Recent research suggests that nearly 3 percent of Americans now have a true food allergy, with about six percent of children under three being allergic to foods such as peanuts, eggs, milk, and shellfish. Researchers, in an attempt to find a reason for the increased rate, are now looking to the possibility that food sensitization may actually occur during pregnancy.
Children with Egg or Milk Allergy Have Greater Risk of Peanut Allergy
In the past, the American Academy of Pediatrics advised women to avoid highly allergenic foods during pregnancy if they had a family history of allergies. At the time, there was evidence that in-utero exposure might contribute to the fetal immune system response that could lead to an allergic reaction after birth. But in 2008, the AAP rescinded that recommendation as more studies indicated that avoidance of such foods did not reduce the incidence of food allergies.
A new study, led by Dr. Scott Sicherer of the Jaffe Food Allergy Institute at the Mount Sinai School of Medicine, included 503 infants between the ages of three and 15 months who showed signs of food allergy – primarily eggs and milk – or had significant eczema (sometimes caused by food allergies). The group focused on these children, as they are more likely to develop reactions to peanuts as well. (Most had not yet tried a peanut.)
The scientists found that children whose mothers ate peanuts more than twice a week while pregnant had higher levels of antibodies to peanuts than those who ate less. More than a quarter of the children displayed a strong reaction in a “peanut sensitivity” test. Consuming peanuts while breastfeeding, however, did not appear to significantly affect test results.
While this does not necessarily mean that the babies will become allergic, it is a strong sign that they are at greater risk, says Dr. Sicherer. “The next question parents might ask is, ‘Are these results enough to change the recommendation that mothers should not worry about eating peanuts during pregnancy?' And the answer is no,” says Sicherer. "Studies have fallen on both sides of this. It is hard to know what is right or if there is any definitive influence."
His group will continue to study the babies to determine how many actually go on to develop a peanut allergy. The ongoing study is being conducted by the Consortium of Food Allergy Research as part of a $29.9 million grant from the National Institutes of Health.
Scott H. Sicherer, Robert A. Wood, Donald Stablein, Robert Lindblad, A. Wesley Burks, Andrew H. Liu, Stacie M. Jones, David M. Fleischer, Donald Y.M. Leung, Hugh A. Sampson. Maternal consumption of peanut during pregnancy is associated with peanut sensitization in atopic infants. Journal of Allergy and Clinical Immunology, 2010; DOI: 10.1016/j.jaci.2010.08.036