The purpose of this study was to evaluate the association between oral health and asthma/allergic rhinitis/atopic dermatitis in a large representative Korean adolescent population.A total of 136,027 participants (aged 12-18 years old) were selected from the Korea Youth Risk Behavior Web-based Survey 2014 to 2015. The subjects' history of asthma, allergic rhinitis, and atopic dermatitis was determined by inquiring whether they had been diagnosed by a medical doctor within the previous 12 months or throughout life. Participants were asked if they had experienced the following 6 symptoms regarding oral health in the past 12 months: "chipped or broken tooth," "toothache when eating or drinking," "throbbing and sore tooth," "sore and bleeding gums," "pain in the tongue or inside the cheeks," and "unpleasant breath." The participants were divided into 3 groups according to the number of oral health-related symptoms as follows: good oral health (symptoms = 0), moderate oral health (symptoms = 1), and poor oral health (symptoms = 2-6). Multiple logistic regression analyses calculated the adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for asthma/allergic rhinitis/atopic dermatitis within the past 12 months and throughout life among groups with oral health-related symptom groups.Older age, female sex, fewer days of physical activity, lower parental economic level, lower parental education level, smoking, and frequent alcohol consumption were associated with poor oral health (each P < .001). The aORs for asthma/allergic rhinitis/atopic dermatitis were 1.48 (95% CI = 1.34-1.63, P < .001), 1.42 (95% CI = 1.36-1.47, P < .001), and 1.35 (95% CI = 1.28-1.43, P < .001), respectively, in the poor oral health group compared to the good oral health group.Poor oral health was significantly correlated with the prevalence of asthma/allergic rhinitis/atopic dermatitis within the past 12 months and throughout life in Korean adolescents. Based on our comparative data, oral health-related education may be considered to adolescents with allergic disease for good oral health.