The prevalence of allergic rhinitis of study subjects by ages (n = 3366) Allergic rhinitis Age Yes No P n% n% 6th Grade (n=1011) 142 14, 05 869 85, 95 0, 55 7th Grade (n=748) 115 15, 37 633 84, 63 8th Grade (n=847) 133 15, 70 714 84, 30 9th Grade (n=760) 125 16, 45 635 83, 55 Tổng 515 15, 3 2851 84, 7 Comment: The above table results showed that the prevalence of rhinitis at the age of 11 - 12 years (6th Grade) was 14.05%; at the age of 13, 14, and 15 years old (7, 8, 9th grades) were 15, 37; 15.70 and 16.45% respectively.