New Research Suggests Environmental Factors at Work in Allergenic Rhinitis and Food Allergies

Here’s a closer look at some of the latest research on the role of environmental exposures and what it may mean for otolaryngologists treating allergic rhinitis and related conditions.

Building Evidence

A study published last December analyzed data from the National Health and Nutrition Examination Survey (NHANES) and looked at 2,211 participants aged 6 years and older. The researchers concluded that excessive use of specific pesticides may be contributing to the increasing incidence of food allergies in the U.S. (Ann Allergy Asthma Immunol. 2012;109:420-425). Additionally, they found that dichlorophenol exposure was associated with sensitization to food allergens. Specifically, the study participants who were in the top 25 percent for urine levels of dichlorophenol metabolites were more likely to be sensitized to one or more food allergens. Conversely, inhalant allergies did not correlate to dichlorophenol exposure.

Dichlorophenols are present in pesticides and herbicides used on food crops and insecticides used in moth balls, said study co-author Elina Jerschow, MD, a physician and researcher in allergy and immunology at the Albert Einstein College of Medicine and Montefiore Medical Center in New York. They’re also present in trace amounts in drinking water, but Dr. Jerschow doesn’t think this is a significant exposure. “Dichlorophenols are only by-products in the water,” she said. “Their levels are strictly regulated and extensive effort is made to prevent their presence in tap water.” Further, she said, bottled water has no such requirements.

The link between pesticides and allergic rhinitis and asthma has also been noted in farmers and pesticide applicators in several countries, Dr. Jerschow said. She and her coauthors offer one possible explanation for the results that lines up with the hygiene hypothesis. Instead of taking children away from the farm and all its attendant microbial exposures, pesticides are taking the microbes away from the farm—at least those microbes important in priming the human immune system.

The strengths of the NHANES study are its large study population and its use of urinalysis to assess concrete evidence of dichlorophenol exposure. No causal link can be inferred from the association, however; that would require a prospective study, Dr. Jerschow said. Finding people who are not exposed to pesticides, treated water or swimming pools would be difficult, and following them for many years might not be feasible.

Chlorine and PAHs

Another recent report out of Belgium, published in November 2012, concluded that sensitization to dust mites in early life is associated with nasal epithelial defects, and that the nasal barrier function can be negatively modulated very early in life by environmental stressors such as pool chlorine (Sardella A, Voisin C, Dumont X, Marcucci F, Bernard A. [Published online ahead of print Nov. 20, 2012.] Pediatr Pulmonol).