While cleanliness in the home is no longer considered a risk factor for allergies, environmental factors can play a role in the development of their immune system and allergic conditions.
“Children that are born in a farming environment are much less likely to have asthma, eczema and allergies,” says Brough. “That’s thought to be due partly to the food that they’re eating and partly to their exposure to bacteria that are in stables.”
A study carried out in South Africa concluded that exposure to farm animals protected toddlers aged 12-36 months from allergic outcomes.
Research on Amish children raised on farms in Indiana provides an even more detailed picture. The Amish are a farming community of Swiss descent, who typically live in large families and follow a traditional bug lifestyle, such as avoiding the use of electricity, and using horse-drawngies instead of cars. The researchers compared the Amish children to Swiss children raised on farms, and also to Swiss children who did not live on farms.
All of these children shared a similar genetic background, but their allergy and asthma rates were very different. The Amish children had the lowest rates of asthma and allergies, while the Swiss children not raised on farms had the highest, comparable to general rates in the US. The Swiss farm children’s rates were in the middle.
The results suggest that lifestyle rather then genetics play a determining role in the development of asthma and allergies, and especially that being in close contact with animals helps. The reason for the difference between the Amish and Swiss farm children was not entirely clear, and may be to do with the size of the families, according to the study.
“In this rural environment exposure to livestock is the strongest protective factor,” the researchers said. “In urban communities, where animal contact is rare, risk factors include caesarian section, and protective factors include consumption of fermented milk products.”
Birth and gut health
Research suggests that there is a link between how a baby is born, their gut bacteria, and later food sensitivities. Babies delivered by vaginal birth, and exposed to their mother’s vaginal and intestinal bacteria in the process, have been found to have higher gut bacterial counts than those delivered by caesarean section. A study by Canadian researchers established a link between children born via caesarean section and peanut sensitivity in infants. These children had persistently low levels of bacteroides – a type of bacteria critical to the development of the immune system – in the first year of their life, the study noted. The babies with low bacteroides were found to have a threefold increase in their risk of developing peanut sensitivity by the age of three.
“It all boils down to the gut microbiome,” says Brough. “We know that children with food allergies have a different gut microbiome to children without them.”
Many mothers who have caesarean section are given antibiotics after the birth, to prevent infection of the wound. While this is important for the mother’s health and recovery, Brough says it can have a negative side effect: “We know that exposure to antibiotics in the first couple of weeks of life increases the [baby’s] risk of eczema.”
This does not mean babies born via caesarean section will definitely develop allergies – and as the LEAP study shows, they can benefit from preventative strategies. But it may shed a useful light on the root causes of allergies.
Growing out of allergies
I luckily outgrew my milk and egg allergies, but am still unable to eat nuts of any kind. This appears to be common. Roughly 80% of children will grow out of their milk and egg allergies, says Kelleher. “But unfortunately only around 20% grow out of a nut allergy.”
“Although allergies to milk, eggs, wheat and soy often resolve in childhood, children appear to be outgrowing some of these allergies more slowly than in previous decades, with many children still allergic beyond the age of five,” says Bufford. Allergies to peanuts, tree nuts, fish and shellfish are generally lifelong, she says.
But even for these allergies, there are treatment options emerging. Immunotherapy, which desensitises the body to an allergen, is a particularly promising treatment. Immunotherapy drugs have been found to induce remission of peanut allergy. In a recent clinical trial in the US, giving peanut oral immunotherapy to highly allergic children aged one to three years – under close medical supervision – desensitised most of them to peanuts and induced remission of peanut allergy in one-fifth. This kind of immunotherapy is different from the preventative steps for babies, and is carried out by experts at specialized medical centers, not by the parents themselves.
Although food allergies are rising rapidly around the world, we are finally starting to understand how to effectively treat them, and prevent them altogether through early intervention.
I know just how life-changing these scientific developments can be. It means that future generations of young children can enjoy carefree play dates and birthday parties, without the risk of becoming incredibly unwell, and that their parents are not plagued by constant fears about hidden allergens.
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