Are pesticides and food allergies linked?
People who
are exposed to higher amounts of chemicals used to chlorinate water and kill
crop pests are also more likely to suffer from food allergies.
The new
finding doesn't prove or even suggest that pesticides or water chlorination
cause food allergies. But it's possible that a class of chemicals called
dichlorophenols could alter the population of microbes in the human body, in
turn influencing the immune system's reaction to food triggers.
"Both
environmental pollution and the prevalence of food allergies are increasing in
the United States," said lead author Elina Jerschow, a practicing
allergist in New York City. "The results of this study suggest that these
two phenomena might be linked."
In the
United States, food allergies affect between 1 and 3 percent of adults and
between six and eight percent of children, said Dr. Clifford Bassett, an
allergist in New York City and spokesperson for the American College of
Allergy, Asthma and Immunology. And bad reactions to foods have grown more common
in recent years, with as much as a 20 percent increase in kids in the last
decade.
In an
attempt to help explain those trends, Jerschow and colleagues turned to
dichlorophenols, which get into our bodies when we drink chlorinated water,
come into contact with pesticides that contain them or breathe contaminated
air.
Dichlorophenols
are designed to kill microbes, making them a possible player in support of the
hygiene hypothesis. The theory proposes that keeping our environments too clean
can backfire, causing the immune system to over-react to potential allergens.
In other words, exposure to dirt and germs may help reduce the risks of
allergies, especially for young children. Anything that kills germs, then, might
have the potential to raise allergy risks.
Using data
collected by the U.S. National Health and Nutrition Examination Survey (NHANES)
in 2005 and 2006, the researchers looked at concentrations of a variety of
dichlorophenols in the urine of more than 2,200 people, ages 6 and older. They
also looked at blood-test results indicating allergies to peanuts, eggs, milk
or shrimp.
People with
the highest levels of dichlorophenols were 80 percent more likely to have food
allergies compared to people with the lowest levels, the researchers reported
today in the journal Annals of Allergy, Asthma and Immunology.
It's far too
soon to conclude that pesticides or chlorinated water cause or increase the
risk of allergies. Instead, Bassett said, the new study offers an intriguing
new line of study that's worth pursuing.
"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,"
Bassett said. "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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