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American Academy of Allergy, Asthma & Immunology Annual Meeting
March 21, 2011
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Oldest children in family face highest risk for allergic conditions

Children born first in their family may be more likely to suffer from particular allergic conditions, according to research presented at the 2011 Annual Meeting of the American Academy of Allergy, Asthma & Immunology in San Francisco.

“It has been established that individuals with increased birth order have a smaller risk of allergy. However, the significance of the effect may differ by allergic diseases,” Takashi Kusunoki, MD, PhD, a researcher of the study, said in a press release.

The results of the study indicate that there was no significant difference in the prevalence of asthma or atopic dermatitis according to birth order. However, the prevalence of rhinitis, conjunctivitis and food allergy decreased significantly as birth order increased; the prevalence of food allergy was 4% in firstborn children, 3.5% in second-born children and 2.6% for children born later. The researchers said as birth order increased, the prevalence of wheeze in infancy increased significantly, whereas the prevalence of food allergy decreased significantly.

When looking specifically at the presence of food allergy in the children during infancy, the same effect was also observed. The incidence of food allergy decreased significantly as birth order increased. Therefore, the researchers said this birth order effect may have a prenatal origin.

Kusunoki and colleagues in Japan looked at the significance of the birth order effect on the prevalence of asthma, atopic dermatitis, allergic rhinitis, allergic conjunctivitis and food allergy. Parents of more than 13,000 children aged 7 to 15 years completed a survey. The data was then examined and the incidence of each allergic disease was compared with birth order.

“Further evaluation should shed light on the role of pre-, peri- and post-natal circumstances on the development of childhood allergy,” Kusunoki said.

For more information:

  • Kusunoki T. #525. Presented at: 2011 Annual Meeting of the American Academy of Allergy, Asthma & Immunology; March 18-22; San Francisco.
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