The prevalence of food allergies, an abnormal immune response to a food that is harmful to the body, continues to rise. The Centers for Disease Control and Prevention (CDC) estimates food allergies affect up to 15 million people including one in 13 children in the U.S.

A recent study indicates that people exposed to higher levels of certain germ- and weed-killing chemicals may be more likely to develop food allergies. Researcher Elina Jerschow, M.D., an allergist at Montefiore Medical Center, investigated the chemicals called dichlorophenols (DCPs), which are created by the breakdown of common pesticides, including chlorinated chemicals used to purify drinking water. DCPs also can be found in moth balls, air fresheners, deodorizer cakes in urinals, and certain herbicides sprayed on crops.

Jerschow speculated that increased protection from germs might somehow be lowering the body's tolerance to foods. The 'hygiene hypothesis,' a medical theory originally proposed thirty years ago, suggests the cleaner our environment, the sicker we become, since our immune system has been robbed of the opportunity to meet and fight off invaders. Using data collected by the National Health and Nutrition Examination Survey (NHANES), Jerschow compared levels of the chemicals in urine to antibodies to foods in the blood. People can be sensitive to certain foods without having any problems when they eat, so Jerschow's method of measuring food allergies is not perfect, though it serves, roughly, as accurate.

People with the highest levels of the chemicals were nearly twice as likely to show sensitivity to at least one food compared to those with the lowest levels of those chemicals, Jerschow found. Of the 2,211 people included in the study, most had detectable levels of DCPs in their urine. About 400 showed sensitivity to at least one food, like peanuts, eggs, or milk. More than 1,000 people were sensitive to an environmental allergen, like ragweed or pet dander. Participants who had been exposed to two dichlorophenol metabolites or more were more likely to have one or more food allergies than those with no or less exposure. They were also 61 percent more likely to be allergic to a food and environmental allergen at the same time.

"Previous research indicated that 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," Jerschow wrote.

Meanwhile, the number of children affected by allergies continues to grow.

Rising Trend

Among children under 17 years old, the prevalence of food allergies increased from 3.4 percent in 1997-1999 to 5.1 percent in 2009-2011, according to the CDC. No significant trend emerged in the number of cases of respiratory allergies during the same periods, although respiratory allergies remain the most common type of allergy among children: 17 percent in 2009-2011. Hispanic children had a lower prevalence of food allergy (3.6 percent) and respiratory allergy (13.0 percent) compared to non-Hispanic white and non-Hispanic black children.

Eight types of foods account for 90 percent of all food-allergy reactions: cow's milk, eggs, peanuts, tree nuts (such as walnuts, pecans, hazelnuts, almonds, cashews, pistachios, and macadamia nuts), fish, shellfish, soybeans, and wheat. Symptoms of an allergic reaction to food can range from mild to sudden and severe, and commonly include one or more of the following:

  • Hives
  • Tingling in the mouth
  • Swelling in the tongue and throat
  • Difficulty breathing
  • Abdominal cramps
  • Vomiting or diarrhea
  • Eczema or rash
  • Coughing or wheezing
  • Loss of consciousness
  • Dizziness

Although food allergies are often mild, they are the most common cause of anaphylaxis, a severe, potentially fatal allergic reaction, in which symptoms affect several areas of the body and may threaten breathing and blood circulation. For this reason, it is important that their cause and increasing prevalence be understood. Different, though related, research might lead to answers.

Pesticides and Parkinson's Disease

Just this month, researchers at the Istituti Clinici di Perfezionamento in Milan published results of an investigation into the risk of Parkinson's disease (PD) and its association with exposure to pesticides and solvents. They examined prospective cohort and case-control studies providing risk and precision estimates relating PD to exposure to pesticides or solvents or to proxies of exposure that were considered eligible. A total of 104 studies/3,087 citations fulfilled the researchers' inclusion criteria for meta-analysis.

The researchers found that PD was associated with farming and the association with pesticides was highly significant in the studies in which PD diagnosis was self-reported. In high-quality case-control studies, PD risk was increased by exposure to any-type pesticides, herbicides, and solvents with the increase in risk ranging between 33 percent and 80 percent. Specifically, exposure to paraquat or maneb/mancozeb was associated with about a two-fold increase in risk. No association was observed with fungicides, rodenticides, organochlorines, and organophosphates. Regarding specific chemicals, the researchers observed about a two-fold increase in risk for exposure to paraquat, while no association was found with exposure to dichloro-diphenyl-trichloroethane (DDT) or tomaneb or mancozeb. PD was also associated with any of the proxy conditions of exposure to organic pollutants investigated; the increase in risk ranged between 30 percent and 34 percent. Finally, the risk associated with rural living was found to be significant: a 1.5-fold increase.

The researchers concluded their results support the hypothesis that exposure to pesticides or solvents is a risk factor for PD. "Further prospective and high-quality case-control studies are required to substantiate a cause-effect relationship," the authors wrote, indicating that future studies should focus on specific chemical agents.

Sources: Jerschow E, McGinn AP, de Vos G, et al. Dichlorophenol-containing pesticides and allergies: results from the US National Health and Nutrition Examination Survey 2005-2006. Annals of Allergy, Asthma and Immunology. 2012.

Pezzoli G, Cereda E. Exposure to pesticides or solvents and risk of Parkinson disease. Neurology. 2013.