Prevention of Allergy in 2008
Sicherer SH and Burks AW. Maternal and infant diets for prevention of allergic diseases: Understanding menu changes in 2008. J Allergy Clin Immunol: 2008;122:29-33.
Summary for the AAIA Newsletter:
The purpose of this editorial by Sicherer and Burks is to describe how the American Academy of Pediatrics (AAP) has changed its recommendations for prevention of allergy in infants at high risk of developing allergies, based on updated evidence. In addition, the authors speculate on future directions in this area, and provide some practical advice on how decisions may need to be individualized in certain scenarios (e.g. having an older sibling with peanut allergy).
In 2000, the AAP defined high risk infants as those who have two parents (or one parent plus one sibling) with allergy. It suggested that there may be benefit from avoidance of peanut during pregnancy, as well as avoidance of peanut and tree nuts in the mother's diet while breastfeeding. For the young child, it suggested delay of dairy until 12 months of age, egg until 2 years, and peanuts, nuts, fish until 3 years.
In early 2008, the AAP published an updated set of recommendations, which are very similar to European recommendations that have been available for years. The AAP changed their definition of high risk to describe an infant with either one parent or one sibling with allergy, making the definition less strict. Most significantly, it has stated that there is a lack of evidence for doing anything beyond exclusive breastfeeding for 4 to 6 months (or use of a hypoallergenic formula if one cannot exclusively breastfeed). In other words, there is no good reason from an allergy point of view for mothers to avoid any foods during pregnancy or while breastfeeding. Similarly, there is no good reason for young infants to delay any specific foods beyond 6 months of age (including egg, peanut, etc) from an allergy perspective.
What has not changed is that both the 2000 and 2008 AAP recommendations have supported use of exclusive breastfeeding for at least 4 to 6 months in high risk infants, which has been shown to have a preventive effect against eczema and cow's milk allergy. This would also mean avoiding any solids until 4 to 6 months of age. If not breastfeeding or if supplementing during the first 4 to 6 months, use of an extensively hydrolyzed casein formula (or a partially hydrolyzed whey formula, although it may be less effective) instead of cow's milk or soy formula is recommended.
In the last section of their editorial, Sicherer and Burks recognize that the 2008 AAP recommendations are a reflection of the limitations of currently available data on prevention, since they focus on explaining what doesn't appear to work rather than giving a lengthy “to-do list”. They comment on current thoughts that delay of foods such as peanut by mouth may be increasing the chance of developing peanut allergy due to a missed opportunity for oral tolerance when young. Furthermore, delay of peanut by mouth may be increasing the odds of early skin contact with peanut, a route of exposure which is suspected to increase the risk of developing peanut allergy. Although these are intriguing thoughts, Sicherer and Burks do make it clear that they are not ready to advise parents to start peanut butter by mouth for their infant at 6 months of age, since the whole situation is still so unclear. It is hoped that studies such as the "Learning Early About Peanut allergy" study in the UK will provide us with further direction. In the meantime, Sicherer and Burks advise individualizing decisions about when to introduce specific foods such as peanut in the young child, through a discussion of the evidence available and consideration of unique factors for the family of concern. An example would be having an older sibling with peanut allergy, which may cause some to prefer either avoiding peanut for the entire family including the younger sibling (for simplicity), or waiting until an allergy assessment for the younger sibling has taken place. It has been shown that a young sibling's risk of peanut allergy is increased by having an older sibling with peanut allergy. To conclude, the authors identify that much more research on prevention is needed.
Edmond S. Chan, MD, FRCPC
Clinical Assistant Professor
Division of Allergy, Department of Pediatrics
University of British Columbia
from Allergy & Asthma News, Issue 4 2008