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Scientists looking at new theories on peanut allergy

By Jane E. Brody
New York Times
LIFE FAM-PEANUTS-PREGNANCY 3 LA
Kirk McKoy - MCT
The prevalence of peanut allergy among children in the United States has risen more than threefold, to 1.4 percent in 2010 from 0.4 percent in 1997. Most people with an allergy to peanuts are also allergic to one or more tree nuts, such as walnuts, pecans or almonds.

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  • A change of view on peanut allergy

    The prevalence of peanut allergy among children has risen threefold since 1997, though researchers don’t know why. In 2000, pregnant and nursing women were advised to avoid eating peanuts, especially if allergies ran in the family. And new mothers were told not to give babies peanuts before age 3, when digestive systems are more fully developed. But that advice did nothing to curb the climb in peanut allery, and it was abandoned in 2008. Today, the thinking is exactly the opposite: The tiny amounts that may enter the baby’s circulation when a pregnant or nursing woman eats peanuts might actually induce tolerance, not sensitization. Still, experts say more research is needed.



Peanut allergy has become a nemesis for increasing numbers of children and parents in recent years, forcing them to maintain nut-free households and prompting many schools to ban a childhood staple, peanut butter, from the lunchroom.

When a child is allergic to peanuts, families must closely monitor everything the child eats, because accidental consumption of peanuts could prove fatal. Many airlines no longer offer peanuts for fear that an allergic passenger might inhale peanut dust and suffer a life-threatening reaction at 30,000 feet.

The prevalence of peanut allergy among children in the United States has risen more than threefold, to 1.4 percent in 2010 from 0.4 percent in 1997. Most people with an allergy to peanuts are also allergic to one or more tree nuts, such as walnuts, pecans or almonds.

Some cities have nut-free bakeries that sell products safe for allergic children, who can bring their own special, albeit expensive, cake or cupcake to a party.

Don’t forget the EpiPen

While experts doubt the necessity of some extreme measures taken to prevent indirect exposure to peanuts, the danger to someone with a peanut allergy who eats them is unquestioned.

The potentially fatal reaction, called anaphylaxis, can occur with a child’s first exposure to peanuts: itchiness, swelling of the tongue and throat, constriction of the airway, a precipitous drop in blood pressure, rapid heart rate, fainting, nausea and vomiting.

Unless the reaction is stopped by an injection of epinephrine (adrenaline), anaphylaxis can kill. In one infamous instance in 1986, Katherine Brodsky, 18, a freshman at Brown University with a known nut allergy, died after eating chili that a restaurant had thickened with peanut butter.

Today, everyone with a peanut allergy is advised to carry an EpiPen for emergency treatment.

New research

Ideally, allergists would like to prevent the development of peanut allergy in the first place. Experts had thought that one way would be to keep fetuses and breast-fed babies from exposure to peanut protein by restricting consumption by pregnant and nursing women.

Various studies had suggested that early exposure to peanut protein by infants with allergic tendencies could sensitize them and lead to a serious peanut allergy.

But this advice did nothing to curb the steady climb in peanut allergies, and it was abandoned in 2008.

Today, the thinking is exactly the opposite. Instead of restricting exposure to peanut protein by unborn or nursing babies, the tiny amounts that may enter the baby’s circulation when a pregnant or nursing woman eats peanuts might actually induce tolerance, not sensitization.

In a recent study, researchers found that children whose nonallergic mothers had the highest consumption of peanuts or tree nuts, or both, during pregnancy had the lowest risk of developing a nut allergy. The risk was most reduced among the children of mothers who ate nuts five or more times a month.

The researchers, led by Dr. A. Lindsay Frazier of Dana-Farber/Children’s Hospital Cancer Center in Boston, wrote: “Our study supports the hypothesis that early allergen exposure increases the likelihood of tolerance and thereby lowers the risk of childhood food allergy.”

According to an accompanying editorial by Dr. Ruchi Gupta, an associate professor of pediatrics at Northwestern University, “some studies actually showed that avoiding peanuts during pregnancy increased the risk of a child developing peanut sensitization.”

In her editorial, Gupta emphasized that further research was needed to understand how maternal diet affects the development of food allergies and “why more and more children are developing food allergy and how we can prevent it.”

But for now, she said, “pregnant women should not eliminate nuts from their diet, as peanuts are a good source of protein and also provide folic acid,” which can help prevent neural tube defects.

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