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Food advice could be peanuts: early exposure seems to lessen the risk of nut allergy.

Consuming peanuts in infancy appears to lessen, not increase, a child's risk of developing a peanut allergy later, British researchers report in the November Journal of Allergy and Clinical Immunology.

The findings clash with some pediatric recommendations of the past decade--parents have been told to avoid feeding peanut products to infants. The new study suggests that early exposure to peanuts, in the form of eating peanut butter, might induce tolerance and head off the aberrant immune response that underlies an allergic reaction.

"This work is extremely thought-provoking and raises the possibility that an approach of trying to avoid peanuts may be the wrong thing to do," says Robert Wood, an immunologist and pediatric allergist at Johns Hopkins University in Baltimore.

Allergist Gideon Lack of King's College London and his colleagues distributed food allergy questionnaires to thousands of families in Britain and Israel in 2004 and 2005. The research team analyzed nearly 9,000 responses, which contained data on roughly 4,000 Jewish children in North London and 4,500 Jewish children in Tel Aviv.

The researchers chose Jewish children in both countries to limit genetic differences between comparison groups.

Peanut allergies showed up in 0.17 percent of the Israeli children and 1.85 percent of the British children, an 11-fold difference in risk. Even after the researchers accounted for age differences between the groups, and for the prevalence of other food allergies and allergic reactions such as rashes or asthma, the British kids were still nearly six times as likely to have a peanut allergy. Among primary school children the risk was nearly 10-fold.

To assess what "first foods" are given to babies in England versus in Israel, the researchers gave questionnaires to mothers visiting clinics with children ages 4 months to 24 months--distributing 99 surveys to Israelis and 77 to Britons. These surveys detailed when the babies first received cow's milk, peanuts, other nuts and eggs.

The results revealed that early peanut consumption was more common in Israel. At 9 months of age, 69 per-cent of Israeli babies had started eating some form of peanuts, whereas only 10 percent of children in Britain had. There was little difference in the age at which other foods were introduced.

"I think there is enough here--even from trying to compare these two different populations--to suggest that peanut avoidance practices in most of the industrialized societies now need to be reexamined," says Wesley Burks, an immunologist and pediatric allergist at Duke University in Durham, N.C.

Peanut allergy in kids has grown in recent decades in Europe, Australia and the United States, where fear has discouraged peanut butter as an early food, the authors note. The average age of onset of the allergy has also decreased in the United States.

In 2000, the American Academy of Pediatrics recommended withholding peanut products until a child reaches 3 years of age. But earlier this year, based on mixed results in ongoing studies, the Academy rescinded that recommendation and reverted to its standard recommendation for introducing non-breast-milk foods--wait until only 4 months to 6 months.

Nonetheless, warnings remain in place in Britain and Australia.

Meanwhile, infants commonly consume peanut products in the Middle East, Africa and Southeast Asia. In all those places, peanut allergy is rare, the authors note.

In 2007, the researchers started recruiting families to participate in a long-term study. Researchers have signed up 640 children under age 11 months, some of whom will be randomly assigned to eat peanut products. When the children reach age 3, the scientists will assess who has developed a peanut allergy. Results are expected by 2014.

Though the cause of peanut allergy remains unknown, it's widely accepted that genetic predisposition plays a part. But genes wouldn't account for the recent increase in allergies since genetics don't change that rapidly, Wood says.

A 2003 study by Lack and his team led to one theory unrelated to genes. The team found that preschool children who were allergic to peanuts were much more likely as infants to have been treated with skin lotion containing peanut oil than were children who didn't have the allergy.

The researchers hypothesized that exposure to peanut protein through the skin laid the foundation for an aberrant immune reaction that resulted in allergy. Researchers continue to investigate this possibility.
Risk of food allergies

Kids in the United Kingdom are 5.8 times
more likely to have peanut allergies than
kids are in Israel.

Relative risk (U.K./Israel)

Peanut       5.8
Sesame       2.7
Hen's egg    1.8
Cow's milk   1.3

Note: Table made from bar graph.


Average age of peanut
allergy onset in U.S.
babies born before 2000   24 months

Average age
in babies born
after 2000                18 months
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Title Annotation:Body & Brain
Author:Seppa, Nathan
Publication:Science News
Geographic Code:1USA
Date:Dec 6, 2008
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