Food allergies are on the rise and researchers are hard at work trying to figure out what causes them. Children, who are more likely to have these allergies, may experience reactions to certain foods that range from mild to life-threatening. No single cause can be found for a food allergy, but there are known risk factors, like family history or having asthma. The latest research is showing that while genetics clearly play a role, environment may have a bigger part to play in developing food allergies.
Food Allergies in Australian-Born Children vs. Immigrants
One interesting study that came out very recently looked at food allergies in Asian children living in Australia. The researchers compared children born there to those who emigrated from Asian countries to Australia. They looked specifically at nut allergies and found that children born in Australia are at a greater risk for them than those that immigrated.
It was a big study, involving 57,000 children, and it suggests that environment may play a much bigger role in developing food allergies than was previously thought. It seems to show that being born in Asia acted like a protective factor against developing a nut allergy, especially when the family immigrated after the child’s early infancy. The researchers also found that the risk for nut allergies was higher for children living in urban areas, another fact that shows environment is a risk factor.
Environmental Factors and Eosinophilic Esophagitis
Another study found that environment is a bigger contributor to the development of eosinophilic esophagitis (EoE) than genetics. EoE is a type of food allergy that leads to a build-up of white blood cells in the esophagus, the tube connecting the stomach and mouth. It makes it difficult and painful to swallow and causes digestive symptoms.
The researchers used identical twins, siblings with exactly the same genetic material, and found that genetics play a role in developing EoE, but not a big one. This means that environmental factors must be more important. Some of those found by the researchers included being allergic to penicillin, having other food allergies, and birth weight differences between twins. EoE is a rarer type of food allergy, but like others that are more common, it is being diagnosed more often.
The Pre- and Postnatal Environments
Important possible sources of environmental risk factors for a child are the mother’s womb and early infancy while being breastfed. The environment that the mother provides, or the factors to which she is exposed, could impact a child’s risk of developing a food allergy. One study found that in mothers with a food allergy, their children were four times more likely to also have a food allergy if they were delivered by C-section. A mother’s age also seems to be a risk factor, with older mothers having more children with food allergies.
Why these are risk factors for allergies is not known. However, for delivery by C-section, researchers believe the increased risk may be related to microorganisms. Children born by C-section as compared to those delivered vaginally have significantly different microorganism colonies in their guts. How this impacts food allergies is still not clear.
Studies are coming in all the time that both fail to find genes for food allergies and that continue to prove the importance of environmental factors. The overall conclusion is that the development of food allergies is complicated and not well-understood. If researchers can continue their work and find the important environmental factors that increase the risk of food allergy development, it could make a big difference for children. If we understand what the factors are, new parents can avoid them to reduce the risk that their children will develop food allergies. Unfortunately, as of now, there is no clear answer.