Table 1.

The characteristics of 25,805 participants

Characteristics		n	%
Gender	Boys	13,013	50.4
	Girls	12,792	49.6
Age (yr)	0-2	3,764	14.6
	3-5	7,828	30.3
	6-8	7,780	30.2
	9-13	6,433	24.9
Second-hand smoke exposure	Yes	5,212	20.2
	No	20,593	79.8
Parental history of allergic disease	Yes	10,212	39.6
	No	15,593	60.4
Allergic symptoms	Current wheeze	1,435	5.6
	Current rhinitis	8,414	32.6
	Current eczema	4,565	17.7
Antimicrobial exposure score	Mean (SD)	14.3	(9.3)