Children of Mexican descent who are born in the US are nearly twice as likely to develop Asthma as those born in Mexico, according to a new report.

“Our study is the first to document variations in the prevalence of Asthma and respiratory symptoms among a national and a representative sample of Mexican American children,” Kamal M. Eldeirawi, from the University of Illinois at Chicago, and colleagues note.

Still, further research is needed to uncover the factors responsible for the variations seen, they add.

The findings are based on a study of 4121 Mexican American children who participated in the Third National Health and Nutrition Examination Survey (NHANES III).

Compared with being born in Mexico, birth in the US doubled the likelihood of having asthma or recent wheeze, the team reports in the Journal of Allergy and Clinical Immunology.

US-born Mexican Americans were also more likely than their Mexico-born counterparts to have a positive skin-prick reaction to a variety of allergens, such as cat, house mite, and peanut. By contrast, they were less likely to have a skin reaction to German cockroaches.

“These findings highlight the need for further studies to examine environmental factors that change by migration and explain the observed differential in the risk of Asthma or wheezing,” the authors conclude.

SOURCE: Journal of Allergy and Clinical Immunology, July 2005.