Pesticides in produce and drinking water may be playing a role in the increasing prevalence of food allergies, according to a new study.
Researchers looked at 2,211 people and found those in the top 25 percent for urine concentrations of chemical dichlorophenols -- used to chlorinate tap water and keep pests off produce -- were also 80 percent more likely to have a food allergy.
"Adults can develop food allergies even though they're not kids anymore," says allergist and study author Dr. Elina Jerschow. "Adult allergies to foods are on the rise. That certainly includes shellfish and fish allergies, but also peanuts. We don't know what influences this development. But having been exposed to dichlorophenols in our study suggests there could be some link."
Researchers believe dichlorophenols may alter the composition of healthy bacteria growing in the human gut, which plays an active role in immune system functioning.
It's the "hygiene hypothesis" -- that allergies result from too few exposures to microbes in our contemporary, sterile environments - with a twist: the anti-bacterial environment might also be found inside the intestines.
The study, published Monday in the journal Annals of Allergy, Asthma and Immunology, doesn't confirm that pesticides necessarily cause allergies or vice versa, but it does indicate a possible association.
"Pesticides, and insecticides in particular, are inherently toxic to human health," says Dr. Kenneth Spaeth, director of the Occupational and Environmental Medicine Center at North Shore University Hospital in Manhasset, N.Y.
"This has been known for a long time in regards to large exposures. However, it is only in recent years that the harmful effects of low-level exposure from pesticides have begun to be revealed."