Genes Cause Most Peanut Allergies

From the WebMD Archives

July 25, 2000 -- Many of us can't imagine life without peanut butter, but peanuts can cause more serious allergic reactions than any other food product. Some have speculated that early exposure to peanuts might increase a child's risk of developing this potentially deadly allergy, but a new study of twins indicates that this is not the case.

"We found that genetics account for 81.6% of the risk of peanut allergy," says study author Scott H. Sicherer, an assistant professor of pediatrics in the division of allergy and immunology at Mt. Sinai School of Medicine in New York.

In recent years, there has been some worry that exposure to peanuts during the first few years of life -- including prenatal exposure of babies whose mothers eat peanut products -- might help trigger peanut allergies. Peanut allergies, which affect some 0.6% of the U.S. population, are seldom outgrown and may be triggered by even the slightest exposure. Managing these allergies is made more difficult by the fact that peanut-based food products are often difficult to recognize.

This study, published in the Journal of Allergy and Clinical Immunology, used the Food Allergy Network newsletter and web site to recruit pairs of twins in which at least one member had a peanut allergy. The researchers interviewed parents or adult twins about the twins' history of allergies and whether they were identical or fraternal.

The 58 pairs of twins included 14 identical pairs and 44 fraternal pairs. Among them were 70 individuals with a history of peanut allergies, experiencing such symptoms as hives, wheezing, repetitive coughing, vomiting, or diarrhea within 60 minutes of eating peanuts.

Sixty-five percent of the identical twins shared an allergy to peanuts, versus only 7% of the fraternal twins -- the same rate found among siblings who are not twins. Sicherer tells WebMD that the 7% rate "is still 14 times higher than the risk of peanut allergy in the general population."

An immediate message from this study is that parents of twins should have both evaluated for the risk of an allergy if one shows signs of sensitivity to peanuts, Sicherer tells WebMD. "Symptoms can range from an itchy mouth after eating peanuts to life-threatening breathing problems," Sicherer says.


Growing public awareness of peanut allergies has prompted calls for dropping peanut butter from school lunch programs, but Sicherer does not support such a ban.

"A 'no food sharing' policy or a special allergy table with more supervision might be more effective," he says. "And remember that it is not easy to avoid peanut exposure. Even in families who are highly trained to avoid peanuts, there is an accidental exposure about once every two years."

"Avoidance is not a complete solution," says Gary A. Bannon, PhD, who developed a mouse model to help researchers study peanut allergies. "Peanut derivatives are an extremely important food product. They are used as protein extenders in many foods, and they are often a hidden component of processed foods."

Bannon, a professor of biochemistry and molecular biology at the University of Arkansas Medical School in Little Rock, says his research group is now working to develop allergy-free peanuts through genetic engineering.


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