Drinking soy milk or soy-based formula does not trigger peanut allergy in children, researchers from the Murdoch Children’s Research Institute have found. Their work challenges the results of an influential previous study.

“Our results show that parents who choose to give their children soy products are not increasing their risk of becoming allergic to peanuts. It’s a myth,” says PhD student and epidemiologist Jennifer Koplin who played a key role in the research.

Peanut allergy is the most common cause in children of the life-threatening allergic reaction known as anaphylaxis. In the past, researchers thought there might be a link between the use of soy products and the development of peanut allergy. The two legumes produce sets of similar proteins, says Koplin, and it was thought this might lead to some amount of cross-reaction in interactions with the immune system.

The new study, however, shows that the association between soy consumption and peanut allergy is coincidental. It occurs because parents whose children are already at higher risk of peanut allergy—due to a family or personal history of cow’s milk allergy—are more likely to give their children soy. The researchers could find no evidence that drinking soy increased the risk of peanut allergy, says Koplin. She analysed data from the Melbourne Atopy Cohort Study which closely followed 620 children from the time of their birth until they were two years old.

The findings, which have been published in the Journal of Allergy and Clinical Immunology, will be used to design future research into the risk factors for peanut allergy.