For a child to develop food allergies, it may take a perfect storm of factors, ranging from genetics to environmental exposures, a new study suggests.
Researchers from the Northwestern University Feinberg School of Medicine, who were studying genetically vulnerable baby mice and the allergens that might trigger sensitivity, were surprised to find many of them did not develop food allergies even after their skin was exposed to peanuts. So the researchers started adding other possible exposures to the mix.
They found mice with the genes for an eczema-like condition would only develop food allergies if they were also exposed to dust mites or mold, had skin contact with the problem foods and were cleaned with soap.
“This is a recipe for developing food allergy,” said lead study author Joan Cook-Mills, a professor of allergy-immunology at Northwestern.
The study results were published in the Journal of Allergy and Clinical Immunology and may help scientists figure out why food allergies are on the rise.
The good news: some of these factors can be changed by parents themselves.
"You can avoid exposing your baby’s skin to peanuts by washing your hands after preparing and eating food," said Cook-Mills. “And if you use soap, rinse it off.”
"Parents these days use products like baby wipes and often don’t rinse the soaps off after wiping down their babies,” Cook-Mills said. “If your grandmother washed you with soap, she always rinsed it off.”
Along with peanuts, foods that can be a problem include:
• eggs
• milk
• wheat
• soy
• fish
• shellfish
• tree nuts
Cook-Mills and her colleagues didn't run an experiment to compare mice wiped down with soap to those that had been only wiped with water, but, she said, the researchers couldn't get the allergens to be absorbed by the mouse pups' skin without wiping them with soap first.
While the study doesn’t prove soap is one of the culprits, “common sense tells me that a substance that decreases the natural protective oils in the skin would facilitate absorption,” said Dr. Maria Garcia-Lloret, an associate professor of pediatrics in the division of allergy and immunology at the David Geffen School of Medicine at the University of California, Los Angeles, and a pediatric allergist at the UCLA Mattel Children’s Hospital. But “that’s all speculation.”
Still, Garcia-Lloret and others do not recommend using soap products when bathing babies in the first month or so because of their potential to dry out sensitive baby skin, making it more vulnerable to eczema and rashes.
The researchers in the new study combined a number of factors and showed food allergy development may “indeed be a perfect storm,” said Garcia-Lloret, who is unaffiliated with the new study.
While cautioning the research is in mouse pups rather than human babies, Dr. Hey Chong said the study does shed light on the complicated process that leads to food allergies. “I think it’s a great proof of concept study,” said Chong, division chief of pediatric allergy and immunology at the Children’s Hospital of Pittsburgh of UPMC. “This could theoretically be one potential mechanism for how babies could react the first time they eat a peanut.”
Earlier studies showed babies who developed eczema were more likely than others to develop food allergies. Experts believe that’s because the condition allows allergens to penetrate the skin.
When a potential allergen is consumed orally, it’s safer, Garcia-Lloret said. "Which is one of the reasons current recommendations are to introduce peanuts orally at an early age."