News article

Peanut Allergy and Breastfeeding

March 25, 2003

Recently, increasing rates of peanut allergy in children have been linked to breastfeeding. Allergies involve a reaction to a substance that someone has been exposed to at least once in the past.

The appearance of documented peanut allergy in very young children has led scientists to wonder how the children may have gotten their first exposure to peanuts.

It is now clear that the substances in peanuts which cause the allergy can be transmitted to the child even before birth, and the substances can also be found in small amounts in the breastmilk of women who have just eaten peanuts. Therefore, sensitization to peanuts can occur both during pregnancy and breastfeeding.

Often people with one allergy may have others, too, and may also have higher rates of eczema and asthma. This predisposition is known as “atopy.” Atopy tends to run in families.

It is unclear whether children with no family history of atopy or allergy are at increased risk of peanut allergy if they are breastfed, as opposed to formula-fed, especially if the mother ate peanuts during pregnancy. Previous data suggest that allergies and atopy tend to be more common in children who are fed formula, as compared to children who were exclusively breastfed - that is, they got no other food or drink besides breastmilk.

Peanuts have become an increasingly important part of the diet in the industrialized world. This probably accounts for at least some of the increasing incidence of peanut allergy. In addition, some foods may contain traces of peanuts, but are not labeled as such.

Of note, a recent study in the New England Journal of Medicine found that peanut allergy was independently associated with intake of soy formula or soy milk. Researchers believe that the association could arise cross-sensitization from certain particles in soy with the particles in peanuts that cause allergy. In other words, researchers speculate that certain particles in soy formula may be similar enough to peanuts that the body may develop an allergy to peanuts, just from exposure to soy formula or soy milk.

If a mother or her pediatrician is concerned about the development of peanut allergy in her child because of a history of allergies in the family, the best current advice would be to avoid peanuts during pregnancy and breastfeeding, and to delay introducing peanuts into the child’s diet. There is currently no evidence to support a recommendation that such women should not breastfeed.

Melissa Bartick, MD, MS
Nashoba Valley Medical Center
Department of Internal Medicine

Kimberly Lee, MD, MS, IBCLC
 Beth Israel Deaconess Medical Center
 Department of Neonatology

References

• Sampson, HA. Peanut allergy. NEJM 2002 Apr 25;346(17):1294-99.
• Vadas P, Wai Y, Burks W, Perelman B. Detection of peanut allergens in breast milk of lactating women. JAMA 2001 Apr 4;285(13):1746-8.
• Frank L, Arian A, Visser M, et al. Exposure to peanuts in utero and in infancy and the development of sensitization to peanut allergens in young children. Pediatr Allergy Immunol 1999 Feb:10(1):27-32
• Lack G, Fox D, et al. Factors associated with the development of peanut allergy in childhood. NJEM 2003, Mar 13;348:977-86