The number of people living with food allergies is increasing. In fact, the Murdoch Children’s Research Institute-led HealthNuts Study found that up to 10% of 12-month olds in Melbourne have a food allergy. We also know that around 2% of adults are affected by food allergy.
The rise in food allergy has happened faster than would be the case if it was due to genetics alone, which means it’s likely that environmental factors are also involved. Researchers have looked at what other environmental or lifestyle factors have been changing at the same time as the increase in food allergy, as this could explain the growing rate of food allergy. The number of babies delivered by caesarean has increased over the past few decades, which is similar timing to the increase in food allergy, so researchers investigated if there is a link.
A possible link was thought to be the microbiome. There are millions of microbes and bacteria in our bodies – this is called the microbiome. The microbiome plays an important role in the development and function of the immune system. Babies get their first microbiome from their mother during birth. If babies are born by caesarean, rather than vaginal delivery, they have less exposure to the mother’s microbiome. Previous research has shown that the microbiome of infants born by a caesarean differs to those born by vaginal delivery.(1) Children with food allergy have also been shown to have a different microbiome compared to children without food allergy.(2) Therefore, researchers thought that the rise in caesareans may partly explain the rise in food allergy.
Researchers from Australia examined this question in the HealthNuts study. They recruited more than 5,000 twelve-month-old babies from council-run immunisation sessions in Melbourne. Babies had skin prick testing to common food allergens and were offered oral food challenges to confirm a food allergy diagnosis. The study data were linked to data collected from hospitals when the babies were born.
In the HealthNuts sample, around 30% of babies were born by caesarean. Reassuringly, researchers found that being born by caesarean delivery did not increase a baby’s chance of developing food allergies.
There was also no difference in the likelihood of food allergy if the caesarean was an emergency or elective procedure, or if it occurred before or after the onset of labour. These findings will help caregivers evaluate the risks and benefits of caesarean delivery. They provide reassurance for mothers who need or choose a caesarean delivery, that there is little evidence their baby will be at an increased risk of food allergy.
Read more about study at the Murdoch Children’s Research Institute website.
Currell A, Koplin JJ, Lowe AJ, Perrett KP, Ponsonby AL, Tang MLK, Dharmage SC, Peters RL. Mode of Birth Is Not Associated With Food Allergy Risk in Infants. J Allergy Clin Immunol Pract. 2022 Aug;10(8):2135-2143.e3. doi: 10.1016/j.jaip.2022.03.031. Epub 2022 May 18. PMID: 35597762.
1. Jakobsson H.E., Abrahamsson T.R., Jenmalm M.C., Harris K., Quince C., Jernberg C., et. al.: Decreased gut microbiota diversity, delayed Bacteroidetes colonisation and reduced Th1 responses in infants delivered by caesarean section. Gut 2014; 63: pp. 559-566.
2. Infant gut microbiota and food sensitization: associations in the first year of life https://onlinelibrary.wiley.com/doi/10.1111/cea.12487