MONDAY, Dec. 3 (HealthDay News) -- Certain chemicals used to purify tap water may play a role in the development of food allergies, a new study suggests.

Researchers from the American College of Allergy, Asthma and Immunology (ACAAI) noted that the chemicals, known as dichlorophenols, are also used to make pesticides and may be found in treated fruits and vegetables.

While the study could not prove a cause-and-effect relationship, it suggests "that high levels of dichlorophenol-containing pesticides can possibly weaken food tolerance in some people, causing food allergy," the study's lead author, allergist Dr. Elina Jerschow, explained in an ACAAI news release. "This chemical is commonly found in pesticides used by farmers and consumer insect and weed-control products, as well as tap water."

The study, published in the December issue of Annals of Allergy, Asthma and Immunology, involved more than 2,200 participants in a U.S. National Health and Nutrition Examination Survey, aged 6 and older. The researchers found that those with sensitivity to one or more foods had higher levels of dichlorophenols in their urine compared to people without such allergies. Overall, more than 400 of these people had a food allergy and more than 1,000 had an environmental allergy.

One expert unconnected to the study said the study does point to the need for further research.

"While the way this study was done does not allow concluding that the pesticides are responsible for the allergies, it certainly raises that possibility and justifies pursuing the kinds of studies that can help sort out if these pesticides are, indeed, the cause," said Dr. Kenneth Spaeth, director of the Occupational and Environmental Medicine Center at North Shore University Hospital in Manhasset, N.Y.

He pointed out that "it is only in recent years that the harmful effects of low-level exposure from pesticides have begun to be revealed. This is of particular concern because low-level exposure is a daily occurrence for all of us from the foods we eat and from its frequent use in gardens, lawns, even inside buildings such as apartments, homes and schools."

According to Spaeth, "it is also understood that the immune system begins developing in fetuses and continues its development through childhood. Therefore, it is plausible that exposure to these pesticides during this development could alter the immune system in ways that could increase the risk of allergies. Until further studies are done, no conclusions can be drawn but there is enough evidence for concern and certainly to further examine the issue."

Study author Jerschow agreed. "Previous studies have shown that both food allergies and environmental pollution are increasing in the United States," he said in the news release. "The results of our study suggest these two trends might be linked, and that increased use of pesticides and other chemicals is associated with a higher prevalence of food allergies."

Switching from tap water to bottled water isn't a solution, the study authors said. "Other dichlorophenol sources, such as pesticide-treated fruits and vegetables, may play a greater role in causing food allergy," noted Jerschow.

One other expert said more study is needed.

"Although more than 1,000 participants had an environmental allergy, which suggests that the rise in environmental allergies -- such as allergies to pollen and mold -- and the increased use of pesticides may be linked, this study should be viewed with caution," said Dr. Luz Fonacier, head of the Allergy & Training Program at Winthrop University Hospital in Mineola, N.Y. "This is an interesting concept that still needs further studies and validation," she said.

Food allergy in children increased 18 percent in the United States between 1997 and 2007, according to the U.S. Centers for Disease Control and Prevention. Among the most common food allergens are milk, eggs, peanuts, wheat, tree nuts, soy, fish, and shellfish. Symptoms of a food allergy can range from a mild rash to a life-threatening response known as anaphylaxis.

Spaeth also offered up the following tips for people looking to reduce their environmental exposure to pesticides:

• Organic foods have lower amounts of pesticides and organic food diets have been shown to lower body levels of pesticides.
• Avoid areas, buildings, yards, gardens where pesticides have been used.
• Try to avoid the use of pesticides in the home.
• Encourage local schools to use Integrated Pest Management, a practice that promotes non-toxic methods of pest control.

More information

The U.S. National Library of Medicine has more about pesticides.