People exposed to higher levels of chemicals used to chlorinate water or to kill pests on crops are at a higher risk of developing food allergies.

This new research doesn’t prove that pesticides or chlorinated water cause food allergies. However, it’s possible that the chemicals – known as dichlorophenols – could alter the microbes within the human body. This, in turn, could affect the way the immune system reacts to certain foods, triggering an allergic reaction.

Elina Jerschow, a New York City allergist who authored the study, explains “Both environmental pollution and the prevalence of food allergies are increasing in the United States. The results of this study suggest that these two phenomena might be linked.”

Food allergies have become increasingly common in recent years, with as much as a 20% increase seen in allergy rates among kids in just the past decade. In an attempt to help explain this trend, Dr. Jerschow and colleagues examined the potential role of dichlorophenols, which enter the body through drinking chlorinated water, breathing contaminated air, or coming into contact with pesticides.

Support for Hygiene Hypothesis

Such chemicals are designed to kill microbes. As such, this new research could support the hygiene hypothesis, which proposes that environments which are too clean could cause the immune system to overreact to potential allergens. Meanwhile, exposure to germs and dirt could help the immune system learn to deal with perceived threats, reducing the risk of allergic reactions. According to this hypothesis, anything that kills germs could have the potential to raise allergy rates.

The researchers used date collected by the U.S. National Health and Nutrition Examination Survey (NHANES) in 2005 and 2006. They examined the concentrations of different dichlorophenols in the urine of more than 2,200 people over the age of 6. They also examined blood test results indicating an allergy to peanuts, shrimp, eggs, or milk, four common food allergies. People who had the highest levels of chemicals in their urine were found to be 80% more likely to have food allergies when compared with people who had the lowest levels of chemicals.

More research must be done before concluding that pesticides or chlorinated water increase the risk of allergies. Instead, says Dr. Clifford Basset, an allergist and spokesperson for the American College of Allergy, Asthma and Immunology, the new study offers a new line of inquiry worth pursuing. He explains “It’s not a slam dunk or proof of cause and effect, but it’s an area of research that’s very thought-provoking and it’s not clear how it will pan out. We’re all kind of scratching our heads to interpret this so we can make the right recommendations to our patients.”

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