Pregnant women who eat peanuts are more likely to have babies who test positive for peanut allergies than women who don't eat peanuts, according to a new study.
That's because the peanut proteins they eat may circulate to the fetus, and cause an allergic response, said study researcher Dr. Scott Sicherer, pediatrics professor at Mount Sinai School of Medicine in New York.
However, the study found infants are only more likely to test positive for the allergy, not necessarily that they have the allergy. The infants in the study did not try eating peanuts to see if they had an allergy, Sicherer said.
"It is true that we think the strong positive tests indicate a high chance of peanut allergy, but it is not the same thing, because many children with a positive test might be able to eat peanuts," he told MyHealthNewsDaily.
Still, the finding bolsters an American Academy of Pediatrics recommendation put forth in 2000 that women with a family history of allergies avoid eating peanut products while pregnant and breast-feeding. That recommendation was withdrawn in 2008 because there wasn't enough scientific evidence.
"Our study shows there is more to be investigated," Sicherer said.
The research was published in the Nov. 1 issue of the Journal of Allergy and Clinical Immunology.
Researchers evaluated 503 infants, ages 3 to 15 months, who had eczema or tested positive for milk or egg allergies, because these factors are associated with peanut allergy. None of the infants had a previous peanut allergy diagnosis.
The researchers asked the mothers whether they avoided peanuts during pregnancy altogether, or if they ate them twice a week, more than twice a week but less than daily, or daily.
Blood tests showed 140 infants had a strong sensitivity to peanuts. The researchers found the more peanuts the mothers ate during pregnancy, the more likely their infants were to test positive for the sensitivity.
The researchers plan to follow the children over time, to see if they develop a peanut allergy, or if they "outgrow" it, Sicherer said.
The same relationship between a mother's consumption and an infant's allergies was observed for egg allergies in the infants, he said.
In another study, Sicherer said being a boy, being non-white and having high positive tests for milk or egg allergies were also risk factors for having peanut allergy.
Just be cautious
Past research has yeilded conflicting results, Sicherer said.
"I have had mothers say they ate a lot of peanuts, and think they caused a peanut allergy, and I have had other mothers say they avoided, and wonder why their child has an allergy," he said.
Often, when another child in the family had a peanut allergy , the family had removed peanuts from the home, and the pregnant mother didn't eat any, he said, but these mothers have wondered whether they should go out of their way to eat some in an attempt to prevent the allergy from developing.
However, there is no definite answer as to what to recommend to mothers, Sicherer said.
Peanut allergy is one of the most common allergies; more than 3 million Americans have some kind of nut allergy, and peanut allergies have more than tripled between 1997 and 2008, according to a study, also by Sicherer, published earlier this year in the Journal of Allergy and Clinical Immunology.
There are a number of theories why peanuts cause allergies in so many people. It's possible peanut proteins are more visible to the immune system than other types of proteins or the oils of emulsified peanut butter are highly allergenic.