A tingling itch here, a scratch there, and a hacking cough are all tell-tale signs that your allergies are about to jumpstart just in time for allergy season. Although seemingly counterintuitive, warm weather leads seasonal allergy sufferers to lament and desire to relocate somewhere cold like Alaska to solve their allergy problems. However, before you pack your bags and head up North, a study published in the Journal of Allergy and Clinical Immunology found allergy prevalence is the same in the U.S., regardless of where you live.
“Before this study, if you would have asked 10 allergy specialists if allergy prevalence varied depending on where people live, all 10 of them would have said yes, because allergen exposures tend to be more common in certain regions of the U.S.,” said Dr. Darryl Zeldin, scientific director of the National Institute of Environmental Health Sciences (NIEHS), in the press release. The study emphasizes people who are prone to developing allergies are going to develop an allergy even if they relocate to more “allergy-friendly” cities. Allergy prevalence based on region is not about developing allergies, but rather what people become allergic to in these different regions.
Every year, the Asthma and Allergy Foundation of America compiles a list of the worst cities for spring allergies and the worst cities for fall allergies, by ranking 100 metropolitan cities. The score of the cities are based on pollen score, the number of people who use allergy medication, and the number of allergy specialists. Although the foundation formulates this list, they explicitly state, “There is no place safe from allergies in America.” If someone has a tendency toward seasonal allergies, they will experience some relief at first, but they will eventually begin to develop sensitivities to the area’s allergens.
At the National Institutes of Health, a team of researchers sought to investigate clustering, sociodemographic, and regional patterns of allergic sensitization. They also examined the risk factors associated with IgE-mediated sensitization, or an allergy triggered by a specific, acquired immune response to a harmless, on-pathogenic antigen. Data was drawn from the National Health and Nutrition Examination Survey (NHANES) 2005-2006, which included approximately 10,000 Americans, to test a greater number of allergens across a wider age range.
Participants who were age 1 or older were tested for serum specific IgEs (sIgEs) to inhalant and food allergens; participants 6 or older were tested for 19 sIgEs, and children aged 1 to 5 years were tested for 9 sIgEs. The researchers compiled the blood serum data to draw conclusions about the allergic sensitization and the risk factors associated with it. Previous NHANES studies used skin prick tests to test for allergies.
The findings revealed the overall prevalence of sensitization did not differ across regions, but regional differences were uncovered when it came to the prevalence of specific types of allergies in early childhood. Those aged between 1 to 5 years from the southern states, such as Texas and Georgia, were reported to have a higher prevalence of allergies than their peers living in other regions. “The higher allergy prevalence among the youngest children in southern states seemed to be attributable to dust mites and cockroaches,” said Dr. Paivi Salo, lead author of the study and an epidemiologist in Zeldin’s research group.
Food allergies were also found to be the highest in the South among participants who were 6 years old and older. While sensitization to outdoor allergens seemed to be most common in the West, indoor allergens and food allergies were most common in the South. Both indoor and outdoor allergies will become more common among children, wrote the study authors, which will eventually lead the overall prevalence of these allergies to fade.
In regards to risk factors for allergies, the study found males, non-Hispanic blacks, and those who avoided pets in the 6 years and older group, had an increased chance of having allergies. Moreover, the researchers found socioeconomic status (SES) did not predict allergies, but people in higher SES groups were more commonly allergic to dogs and cats, whereas those in lower SES groups were more commonly allergic to shrimp and cockroaches.
Allergy sufferers must keep in mind relocating will not help many allergy cases, especially those with seasonal allergies. According to the American Academy of Allergy Asthma & Immunology, about eight percent of people 18 in the U.S. have hay fever. Worldwide, the prevalence of allergic diseases has continued to rise for more than 50 years.
Source: Arbes SJ, Calatrono A, Gergen PJ, et al. Prevalence of allergic sensitization in the United States: Results from the National Health and Nutrition Examination Survey (NHANES) 2005-2006. J Allergy Clin Immunol. 2014.