The cause of this increase in allergies isn’t known. But we do know that the peanut has become ever more ubiquitous in the past 50 years or so, with peanut oil popping up in unexpected places, from cooking sauces to moisturizing cream.
One theory is that eating peanuts in pregnancy might trigger an allergy in the child, especially for children in families with a history of allergies. The American Academy of Pediatrics even went so far as to advise women not to eat peanuts while pregnant. But a few years ago, this advice was withdrawn,* because there’s little strong evidence to back it up.
There are a few things about this study that should give us pause, however. Firstly, the allergy tests used in the study can't tell us for certain whether the babies were allergic to peanuts. These tests can only show whether someone is "sensitized" to peanuts, meaning that their immune system has an abnormal response to the food. To confirm an allergy, the person would need to eat peanuts in a controlled environment to see if they have a true allergic response. This type of test isn't appropriate for babies, but the researchers hope to follow up with the children when they are older.
We also know that people don’t always recall their diets accurately, especially after a period of months. Finally, this type of study can show a link, but cannot prove cause and effect.
What you need to know. There’s still no firm evidence about whether eating peanuts in pregnancy can increase the chances of your child getting peanut allergy. But this latest study suggests there may be something to the theory.
—Anna Sayburn, patient editor, BMJ Group
*links to PDF