Foreign-Born Children Less Likely to Have Allergies than those Native to United States

As spring continues to bring the United State strange temperatures of both hot and cold, followed by stormy weather as we eventually run into summer, allergies run high in certain areas of the country. However, a new study notes that children who moved to the United States are, in fact, at a lower risk of allergies than those who were born in the country.

The study suggests that children who immigrated to the United States were 44 percent less likely to have an allergy condition-including asthma, eczema, hay fever or food allergies-compared to those native born, according to lead researcher Dr. Jonathan Silverberg, a dermatologist at St. Luke's-Roosevelt Hospital Center in New York City. 

These findings support the "hygiene hypotheses," which examines the believe that early exposure to certain germs or infections may protect against some allergies, according to the authors of the study.

Yet another component shows an interesting element all together. Foreign-born children who lived in the United States for more than 10 years were about three times more likely to actually develop an allergy compared to other immigrants who had lived in the country for two years or less, according to the study.

Researchers find that childhood allergies are higher in the United States than many other countries, such as Mexico and China. However, few studies have looked at why allergy risks are smaller among immigrants than U.S. citizens.

The new study was based on information from about 91,800 U.S. children. Parents were asked in a survey in 2007 and 2008 whether a doctor had ever told them that their child had asthma, eczema, hay fever or food allergies.

About 34 percent of children born in the United States had an allergy, compared with about 20 percent of those born outside the country. The link held true regardless of participants' ethnicity, income level or whether they lived in an urban or rural area.

Children born outside the United States were 73 percent less likely to have asthma, 55 percent less likely to have eczema, 66 percent less likely to have hay fever and 20 percent less likely to have a food allergy compared with kids born in the United States.

Children who were born in the United States but whose parents were immigrants also had a reduced risk of allergies.

Foreign-born children who lived in the United States for longer than 10 years were more likely to have eczema or hay fever than those who lived in the country for two years or less.

The new study cannot say why children born in the United States are at greater risk for allergies than those born in other countries.

Silverberg said he suspects that a number of factors, including climate, diet and obesity, play a role in triggering allergies. People with a genetic susceptibility may be at increased risk for developing allergies once they encounter those triggers, he said.

Future studies are needed to better determine what these triggers are, Silverberg said.

The study is published April 29 in the journal JAMA Pediatrics.