(Ivanhoe Newswire) -- A lot has been said about birth order. Firstborn’s are perfectionists and middle children are the most adventurous, right? Well, new research shows there may be some science behind sibling differences -- when it comes to their allergies!

Researchers say firstborn children are at greater risk of developing asthma and allergies because of different conditions they experience in the uterus.

Allergic development is linked to a variation in the DNA of the IL-13 gene. Researchers found among firstborn children, the IL-13 gene variant was associated with statistically significant higher relative risk of having increased cord blood IgE -- an indication of increased allergic response. In skin prick tests up to age 10, the higher risk persisted. Such associations were not seen in children who were not firstborn.
 

“Our findings add to the evidence that allergic reactions are programmed during pregnancy and then affect the disease in later life,” Wilfried Karmaus, M.D., M.P.H., of the University of South Carolina, was quoted as saying. “This finding may partially account for the increasing prevalence of asthma and allergies in children in the last 30 years, primarily seen in the western world, as developed nations’ birthrates continue to decline.”

Researchers also hope to use these results to reduce rates of asthma and allergy in firstborns by changing the conditions in the uterus during first pregnancy. “If we could produce pregnancy conditions for first-born children that are comparable to later-born children, we may be able to prevent 20 to 30 percent of all cases of asthma and allergy,” Dr. Karmaus concluded. “Better understanding the mechanism involved in prenatal priming [of immune development] may offer new and exciting avenues of intervention.”

SOURCE: Presented at the American Thoracic Society’s 2008 International Convention in Toronto, May 16-21, 2008