“I would have guessed that allergies are much more common in the western United States,” said Darryl C. Zeldin, scientific director of the National Institute of Environmental Health Sciences, part of the National Institutes of Health, and a leader of the study. “The bottom line is people are going to be allergic to whatever is in their environment if they’re prone to developing allergies.” Sensitivity to allergies is probably determined by genetics, he said.
In the west, the regional allergy proclivity is to grass, weeds and tree pollen. In the south it’s dust mites, Zeldin said. Half of all residents of urban areas suffer from allergies, while just 40 percent of people in “non-metropolitan” areas are affected by them.
Researchers tested subjects’ blood for antibodies that indicated sensitivities to a wide variety of allergens and looked at data on dust found in the homes of 7,000 people to determine what starts eyes watering in various places. The data was collected during the National Health and Nutrition Examination Survey in 2005-2006, and the study was published last week in the Journal of Allergy and Clinical Immunology.
Demographic categories also made a difference. Non-Hispanic blacks older than five were most sensitive to all allergens tested except eggs and Russian thistle. Among children aged one to five, whites tended to be less prone to allergies than other racial and ethnic groups.
The researchers also noted “clustering” of allergies. People allergic to cats were somewhat more likely to be sensitive to dogs; those who reacted to dust mites were sensitive to two different kinds, and people allergic to proteins in cockroach feces were more likely to be similarly plagued by shrimp. The two creatures are distant relatives, Zeldin said.