Season of birth linked to dust-mite asthma

NEW YORK (Reuters Health) – There appears to be an
association between birth month and sensitization to house dust
mites in asthmatic children, Korean researchers report.

Early exposure to high levels of allergy-triggering
substances is key to the development of hypersensitivities, Dr.
Young Yull Koh, of Seoul National University Hospital and
colleagues write in the medical journal Allergy.

“In fact,” they report, “subjects sensitized to house dust
mites have a significantly higher proportion of births in the
season when house dust mites are most abundant.”

The researchers examined data on 2225 asthmatic patients
between 10 and 16 years of age. A total of 1642 subjects
sensitized to dust mites were identified by skin-prick testing.
Of these, 715 were sensitized only to dust mites and 927 were
sensitized to dust mites and other allergens.

The researchers observed a significant difference in birth
month distribution for asthmatics sensitive only to dust mite.
They were significantly more likely to have been born in August
or September, and to a lesser degree in October. No such
difference was seen in patients sensitized to dust mites and
other allergens.

The team notes that studies of house dust mite allergen
levels in the Seoul area showed that these were highest from
August to October. Similar findings on dust mite abundance and
allergy have been made in England and Denmark.

The investigators suggest that the high exposure to dust
mite allergen in the first few months of life may have a
particular impact in subjects with a high sensitization
threshold who are less likely to become sensitized to other
allergens.

SOURCE: Allergy, October 2005.