Allergies less prevalent in foreign-born Americans

Compared with US-born American children, those born outside the United States are significantly less likely to develop allergic disease, a study in more than 91,600 children aged up to 17 years found. The odds of developing allergic disease significantly increased after residing in the United States for 1 decade or longer, however.

Investigators distributed questionnaires to participants who were enrolled in the 2007-2008 National Survey of Children’s Health, and also conducted parent and child interviews. Analysis of collected data showed that 20.3% of children born outside the United States had any allergic disease compared with 34.5% of native-born children. In particular, children born outside the United States had lower odds of ever or current asthma, eczema, and hay fever.

In addition, children of parents born outside the United States were less likely to have any allergic diseases than those whose parents were native born, including ever and current asthma, eczema, hay fever, and food allergies. An additive effect also was observed, as children of 2 foreign-born parents had lower prevalence of allergic disorders than those with a single parent born outside the United States. In addition, children born outside the United States whose parents were also foreign born were less likely to have any allergic disease than those with US-born parents. Finally, compared with foreign-born children who lived in the United States only 0 to 2 years, those born elsewhere who lived in the United States for longer than 10 years were more likely to develop any allergic disorders (Silverberg JI, et al. JAMA Pediatr. 2013;167[6]:554-560).

Commentary: Children who immigrate to the United States are less likely to have asthma, allergies, and atopic disease than native-born children. Their advantage is diminished if the immigrant children’s parents were born in the United States and decreases the longer they are here. This may be a demonstration of the hygiene hypothesis with allergen exposure in the child’s country of birth decreasing his or her allergic tendency. If that is the case, then either the protective effect of early antigen exposure wanes with time or children are exposed to other more allergenic proteins as they spend time here. -Michael Burke, MD

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