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The white arrow indicates Jeju island in South Korea. (B) The approximate geographical locations of the selected schools (circles) and the pollen counters (white stars) are marked. The skin prick test was performed after informed consent from each student's parents. JC pollen (Greer Laboratories Inc., Lenoir, NC, USA) was diluted with 0.9% saline to a protein concentration of 100 ?g/mL, and the same volume of 50% glycerin was added. Sensitization to an antigen was defined as a mean wheal size that was the same or learn more larger than that of the positive control (allergen/histamine ratio ��1). Atopy was defined as sensitization to one or more aeroallergens tested. The data were excluded when the wheal size for the positive control (histamine 1 mg/mL) was smaller than 2 mm or if a wheal was observed in the negative control (0.9% saline). A questionnaire was designed, which asked whether pollinosis symptoms were present within the last 12 months and in which month they were present. A case of JC pollinosis was defined as one with pollinosis symptoms present during the JC efflorescence season among the JC pollen-sensitized. Burkard 7-day recording volumetric spore traps (Burkard Manufacturing Co., Rickmansworth, UK) were installed in the 2 geographic locations of 126��31'13.67"" E, 33��29'29.27"" N, representative of the NR, and 126��33'18.97"" E, 33��15'11.86"" N, representative of the selleck inhibitor SR (Fig. 1). The drum in the device was harvested weekly at the same time. The trapped pollen was mounted in glycerin jelly and stained. The pollen collected per 24-hour period was identified and counted by an expert at ��400. JC pollen season in each year was defined as extending from the first day when JC pollen was detected on 2 or more consecutive days to the first day when no JC pollen was identified for a full day. Monthly mean temperature data for the two regions were obtained from the database of the Korea Meteorological Administration.5 RESULTS Among the 1,750 questionnaires distributed, 1,524 (87.1%) were returned. Skin prick tests were performed on 1,291 students (73.8%) in April 2010, (-)-p-Bromotetramisole Oxalate and 1,225 participants with valid skin prick tests (607 boys, 49.6%, median age of 13, interquartile range [IQR] 11-16) were included in the final analysis. Among those, 438 (35.8%) were attending elementary school, 458 (37.4%), middle school, and 329 (26.9%), high school. Overall, 569 students (46.4%, boys 52.4%, median age 13, IQR 11-16) resided in the NR, and 656 (53.6%, boys 47.1%) resided in the SR (Table 1). Table 1 Demographic characteristics The sensitization rate was highest for house dust mites followed by JC pollen (17.6%). The participants from the SR showed a higher rate of atopy than those from the NR (50.6% vs. 41.1%, P
