Tuesday, March 22, 2011

Two Significant Allergy Studies

First born children may be at greater risk of food allergies and hay fever than subsequent siblings, reported at the American Academy of Allergy, Asthma & Immunology meeting. Researchers surveyed parents of more than 13,000 school children ages 7 to 15 in Kyoto, Japan about specific symptoms indicative of allergic diseases and analyzed the relationship to birth order in the 11,454 children for whom this factor was known. A clear downward trend in prevalence at school age appeared for the following:

Allergic rhinitis at 30% among firstborns, 26% among secondborns, and 21% among third- and later-born children Allergic conjunctivitis at 27%, 25%, and 21%, respectively
Food allergy at 4%, 3.5%, and 2.5%, respectively

In infancy, eczema declined in prevalence for second- and later-born children compared with those who were their parents' first. The same was true for food allergy in infancy.

Prior pregnancies may change a woman's immunological milieu in ways that affect subsequent children, he suggested. Both agreed that whatever the mechanism, the results likely would generalize to other countries despite Japan's generally lower birth rate and smaller family size.

Pollen Levels Active Beyond Peak of Season

Pollen levels of certain plants, such as grasses and cupressaceae, can appear before or after the peak moment of flowering. This phenomenon is caused by the "resuspension" of pollen, and its dispersal over large distances by wind, and this is of great use in predicting allergies. There is of course a very close relationship between the moment at which pollen is released by plants and the data gathered by the traps used to measure these grains, but this is not always the case. Researchers found delays or advances of up to a week between the time when the pollen of allergenic grass species are present in the air and their flowering period. International Journal of Biometeorology

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