Researchers and the public alike are questioning why food allergies occur in one of every 13 children—equivalent to six million, and growing—in the U.S. A recent study supports the theory connecting early exposure to food allergies to children with skin infections or eczema in their first year of life.
The Hygiene Hypothesis
A "hygiene hypothesis" was proposed to explain why allergies are increasing, in addition to supporting the idea of early exposure to germs, which impact the immune system and reduce the risk of allergic disease.
According to a publication in Allergy and Asthma Proceedings, food allergies had more of a connection to asthma as opposed to hygiene factors like pet exposure. While the hygiene hypothesis is not thoroughly examined for food allergies, it is well recognized in asthma.
Lead author, Ruchi Gupta, M.D., MPH, pediatrician and researcher at Ann & Robert H. Lurie Children's Hospital of Chicago and associate professor of Pediatrics and Medicine at Northwestern University Feinberg School of Medicine, explained the outcome of the study.
"Our results do support the hygiene hypothesis showing that increased number of siblings is protective for food allergy," said Gupta. "The association of food allergy with early skin infection and eczema, however, might shed some light on how food allergies develop. Our findings support the hypothesis that food sensitization might start with exposure through the skin. This might have implications for prevention of food allergies."
Investigating Food Allergies
With 1,359 participants, the study examined individuals as young as birth to 21 years old with and without food allergies.
Additionally, the family-based study included siblings with and without allergies. Having similar genes of the participants helped the study researchers evaluate the impact of different exposures on food allergies and asthma.
The study’s examination in key hygiene factors connected to food allergies and asthma include:
- Antibiotic use,
- Infection history,
- Number of siblings, and
- Pet exposure.
A few maternal child health factors were also assessed during the study such as maternal age at birth, cesarean section, breastfeeding and out-of-home child care.
The only hygiene factors associated with a decrease in food allergy were the number of siblings and care in a child care center.