Let me start off by clarifying there are no guaranteed strategies to prevent allergies, just reduce the risk of developing them. About 20% of people in the US have at least one allergic condition: allergic rhinitis (eg “hay fever”), allergic asthma, eczema, or food allergy. If one parent has any sort of allergic condition, their child will be twice as likely as the general population to develop allergies. If both parents have allergies, well, their children are three times as likely to develop some sort of allergic condition, compared to children of non-allergic parents. For food allergy, specifically, a baby with a nut-allergic older sibling has a 7 times higher risk of developing a food allergy compared to a baby whose older siblings do not have food allergy. Families and doctors alike are anxious to find strategies to reduce this risk.
During pregnancy, many studies have attempted to determine whether avoidance of allergenic foods such as milk, egg, or nuts has an effect on the baby’s development of allergic disease. In general, studies agree that maternal avoidance of milk and egg does not affect the development of allergies in the baby and may cause nutritional deficiencies of Vitamin D or other nutrients in both the mother and fetus. For maternal peanut ingestion, however, the studies are conflicting. Many studies show no association between maternal peanut ingestion and the risk of the baby developing peanut allergy. However, some studies suggest that when mothers ate nuts more than 1-2 times per week, their infants were more likely to develop peanut allergy. Currently, the best advice during pregnancy is probably the old adage, “Everything in moderation.”
Breastfeeding exclusively for 4-6 months is recommended by the World Health Organization and just about every other organization in the world. In addition to other benefits, exclusive breastfeeding may reduce the risk of eczema, wheezing, and cow’s milk allergy. However, if for whatever reason, formula supplementation is given in the first 6 months of life, hypoallergenic formula may reduce the risk of the infant developing eczema, and possibly food allergy or other related allergic conditions. Partially hydrolyzed formulas such as Nestle Good Start cost the same as regular cow’s milk-based formula and may reduce the risk by about 30%. Extensively hydrolyzed formulas such as Nutramigen or Alimentum may reduce the risk further, but are more pricey. Soy formula has not been shown to affect the development of allergies and there isn’t data on the elemental amino acid formulas.
Introducing solids into the baby’s diet is a topic whose recommendations have see-sawed over the past 2 decades. Most pediatricians agree that solids should be introduced once the baby has good head support and muscle control, usually between 4-6 months of age. The story about when to introduce the highly allergenic foods such as milk, egg, nuts and fish into baby’s diet starts back in the late 1990s. Clinical practice guidelines in the US and Europe made common-sense recommendations that high-risk babies should avoid high-risk foods until they were at least 1 year old. However, the incidence of food allergy skyrocketed during the decade these guidelines were in place. At the same time, other studies suggested that early introduction of allergenic foods was associated with a lower rate of food allergy. The guidelines were withdrawn by 2010, but new recommendations awaited further data.
In early 2015, exciting results of an interventional study were announced. Researchers in England found that by introducing peanut into the diet of a high-risk baby between the ages of 4-11 months, the risk of that baby developing peanut allergy was reduced by 86%! Now, this study recruited “high-risk” babies – defined as those having severe eczema and/or egg allergy – and cautiously introduced the first dose of peanut in an observed medical setting after allergy testing and consultation. Allergists and pediatricians are still debating how and when to apply these findings in the real world. This study significantly adds to the growing literature that early introduction of allergenic foods is preferable to a delay beyond 12 months. Current guidance is to start introducing rice or oat cereal, vegetables, and fruit between 4-6 months of age, with a new food every 3-5 days. Once these basic complementary foods are firmly established in the baby’s diet, allergenic foods such as yogurt, eggs, nut butters, and fish can be introduced into the infant’s diet.
Red flags that should prompt a consultation with an allergist before further introduction of allergenic foods includes babies with moderate-to-severe eczema, those who have had an immediate allergic reaction to a food, or those with elevated blood test levels to foods (in general, testing large food panels in the blood are rarely helpful, and often generate a lot of confusion and sometimes unnecessarily restrictive diets). Allergists can also help manage difficult-to-control allergies, asthma, or eczema once they have developed.
In summary, there is growing data about strategies that can help minimize the risk of a child developing allergies. During pregnancy, allergenic foods should be consumed in moderation. Exclusive breastfeeding or use of hypoallergenic formulas may help reduce the risk of developing some allergic conditions. Introduction of allergenic solid foods should not be delayed beyond 12 months of age in most babies.
Susan S. Laubach, MD joined Allergy & Asthma Medical Group and Research Center in July 2011. Originally from Stockton, California, Dr. Laubach majored in Human Biology with honors from Stanford University before undergoing her medical training at the University of California, San Francisco (UCSF) School of Medicine. She trained in pediatrics at Mount Sinai Medical Center in New York, where she founded a Palliative Care service for children with life-threatening illnesses. She then completed a fellowship in Allergy and Immunology at Duke University in Durham, NC where she received extensive training in the diagnosis and management of primary immunodeficiency and food allergy. Prior to joining Allergy & Asthma Medical Group and Research Center, Dr. Laubach conducted research on sublingual immunotherapy (SLIT) for children with peanut allergy, under the direction of Dr. Wesley Burks at Duke University. Dr. Laubach is an active member of the American Academy of Allergy, Asthma, and Immunology; the American College of Allergy, Asthma, and Immunology; the American Academy of Pediatrics; and the American Medical Association. Dr. Laubach and her colleagues at San Diego’s Allergy & Asthma Medical Group are available to help families with food and environmental allergies, as well as asthma.