MONDAY, March 21 (HealthDay News) -- First born children appear to have a higher risk of suffering from certain types of allergies than their siblings, according to a study presented at the annual meeting of the American Academy of Allergy, Asthma & Immunology, held from March 18 to 22 in San Francisco.
Takashi Kusunoki, M.D., Ph.D., of the Shiga Medical Center for Children and Kyoto University in Japan, and colleagues administered a questionnaire dealing with the prevalence of allergic diseases to the parents of more than 13,000 schoolchildren, aged 7 to 15 years, to evaluate the significance of the birth order effect on the prevalence of specific allergic diseases, including bronchial asthma (BA), atopic dermatitis (AD), allergic rhinitis (AR), allergic conjunctivitis (AC), and food allergy (FA).
The investigators found no significant difference in the prevalence of BA or AD according to birth order. However, the prevalence of AR, AC, and FA fell significantly as birth order increased. The researchers determined that the prevalence of FA in children with first, second, and later birth order was 4.0, 3.5, and 2.6 percent, respectively. For those with symptoms in infancy, the prevalence of wheezing increased significantly and food allergy decreased significantly as birth order increased.
"We observed the disease specificity of the birth order effect on allergy among schoolchildren. The present data are the first to show a birth order effect on food allergy. The fact that the effect was also observed for food allergy in infancy suggests its prenatal origin," the authors write.
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