Changes in the positive rate of a scratch test with aging as observed in the same students

A comparison of the data collected in 1989 and 1992 in Shiraoi-cho, Hokkaido

Abstract

Changes in the positive rate of a scratch test with aging were examined in the same students who all underwent a collective physical exmination and a relevant scratch test in both 1989 and 1992 in Shiraoicho, Hokkaido. The subjects consisted of first graders at an elementary school in 1989 who were then in the fourth grade in 1992, and fourth graders in 1989 who were then in the first year of junior high school in 1992. In both groups, the positive rate of the scratch test increased significantly in 1992 in comparison to the results observed in 1989. The increase in the positive rate of the scratch test as the students aged is considered to be due to the duration of the period during which the students were exposed to the allergen.