Food for Thought

By Janet Raloff

Peanuts are a protein-rich snack food packing plenty of vitamins and trace nutrients. However, these legumes can elicit potentially life-threatening immune reactions within the one in 100 American adults who are allergic to them. Rates of peanut allergy are even higher among children. And the really disturbing news: A new study finds that the age at which this common food allergy first shows up is falling.

NOT NUTS. Despite their name, peanuts are legumes akin to soy and peas. However, like true nuts—those that grow on trees—peanuts can cause serious food allergies. Indeed, these tasty legumes are the most common source of food allergy in the United States. iStockphoto

Today, peanut allergy typically emerges in early toddlerhood, a team of Duke University researchers reports in the December Pediatrics. "That's almost a year earlier than what we knew, scientifically, a decade ago, "explains A. Wesley Burks, a pediatric allergist who coauthored the new study.

Although children outgrow many allergies, peanut allergy is not typically one of them. Among people who develop immune reactions to this food, 80 percent retain their allergy for life.

The new study began, Burks says, after Duke immunologists noticed that they were encountering younger patients with peanut allergy. To investigate, the researchers pulled entry records and medical charts for all 140 young patients who had come in with the allergy since 1988. Poring over the records confirmed a fall in age at first diagnosis throughout this period—one that proved more dramatic than expected, Burks told Science News Online.

Nationally, the rate of food allergy appears to be increasing, according to a 2006 report of a National Institutes of Health expert panel. The most striking increase, it noted, has been for peanut allergy, which is also the most common food sensitivity. Because some allergies can be avoided by delaying a child's initial introduction to certain foods, in 2000 the American Academy of Pediatrics recommended that parents "consider" keeping peanuts, tree nuts, fish and shellfish out of the diet of kids under age 3.

Burks acknowledges that most parents aren't aware of this recommendation. On the other hand, most peanut allergy shows up in children that had already exhibited allergic reactions to other foods—typically eggs or milk. Many affected children also had skin sensitivities as infants, such as eczema or atopic dermatitis, and a parent or sibling with allergies, although not necessarily to food.

Against that background, you would think parents of the most vulnerable kids would be especially careful about introducing peanuts into the diet. And they might well have been. Indeed, Burks suspects that most initial introductions to peanuts in his young patients were inadvertent. Either a child encountered items that contained unlabeled traces of peanuts—perhaps a jelly bean, certain flavorings used in medicines, or any of several baby lotions (see Unexpected Sources of Peanut Allergy). Or perhaps the kids encountered peanut allergen in the air when others were eating, handling, or cooking foods that contained the legume.

But for now, Burks' team has no firm leads on why peanut allergies are showing up earlier. The Duke group and others will be probing that in the next few years.

For more information, see this week's Food for Thought column.

References:

Green, T.D. . . . and A.W. Burks. 2007. Clinical characteristics of peanut-allergic children: Recent changes. Pediatrics 120(December):1304-1310. Abstract available at http://dx.doi.org/10.1542/peds.2007-0350.

Hallett, R., L.A.D. Haapanen, and S.S. Teuber. 2002. Food allergies and kissing. New England Journal of Medicine 346(June 6):1833-1834. Extract available at http://content.nejm.org/cgi/content/extract/346/23/1833.

National Institute of Allergy and Infectious Disease. 2006. Report of the NIH Expert Panel on Food Allergy Research. March 13-14. Washington, D.C.: National Institutes of Health. Available at http://www3.niaid.nih.gov/topics/foodAllergy/ReportFoodAllergy.htm.

Further Readings:

Helmuth, L. 1999. Allergy vaccine may take fear out of nuts. Science News 155(April 3):213. Available at www.sciencenews.org/pages/pdfs/
data/1999/15514/15514-04.pdf.

Long, A. 2002. The nuts and bolts of peanut allergy. New England Journal of Medicine 346(April 25):1320-1322. Extract available at http://content.nejm.org/cgi/content/extract/346/17/1320.

Raloff, J. 2003. Unexpected sources of peanut allergy. Science News Online (March 15). Available at http://www.sciencenews.org/articles/20030315/food.asp.

______. 2002. A rash of kisses. Science News 162(July 20):40. Available at http://www.sciencenews.org/articles/20020720/bob9.asp.

______. 1998. The mango that thought it was poison ivy. Science News Online (Aug. 8). Available at http://www.sciencenews.org/pages/sn_arc98/8_8_98/food.htm.

______. 1997. A whiff, a sniff—then asthma. Science News Online (Feb. 1). Available at http://www.sciencenews.org/pages/sn_arc97/2_1_97/food.htm.

______. 1996. Peanut allergy found common and increasing. Science News 150(Sept. 7):150. Available at www.sciencenews.org/pages/pdfs/
data/1996/150-10/15010-10.pdf.

_____. 1996. Family allergies? Keep nuts away from kids. Science News 149(May 4):279. Available at www.sciencenews.org/pages/pdfs/
data/1996/149-18/14918-11.pdf.

Seppa, N. 2003. Tough nut is cracked: Antibody treatment stifles peanut reactions. Science News 163(March 15):163. Available at http://www.sciencenews.org/articles/20030315/fob1.asp.

Sources:

American Academy of Pediatrics
141 Northwest Point Boulevard
Elk Grove Village, IL 60007
Web site: http://www.aap.org

A. Wesley Burks
Division of Pediatric Allergy and Immunology
Duke University Medical Center
DUMC 2644
Durham, NC 27710

National Institutes of Health
National Institute of Allergy and Infectious Diseases
Office of Communications and Government Relations
6610 Rockledge Drive, MSC 6612
Bethesda, MD 20892-6612
Web site: http://www3.niaid.nih.gov