The purpose of the study is to identify the relationships between allergic disease, suicidal ideation, and plans among Korean adolescents. Additionally, we examined the mediating role of short sleep duration. We analyzed nationally representative cross-sectional data from the 12th to 14th Korea Youth Risk Behavior Web-Based Survey; the final sample included 164,725 middle school-aged and high school-aged adolescents (mean age = 15.17 years, standard deviation = 0.13; 51.1% male). Allergic disease was a statistically significant risk factor for suicidal ideation (crude odds ratio [COR] = 1.284, 95% confidence interval [CI] = [1.246, 1.323]) and suicide plans (COR = 1.165, 95% CI = [1.108, 1.224]). Short sleep duration was a statistically significant mediator (p < 0.001). We advised school nurses to assess warning signs of poor sleep--including irritability, depression, sleep problems, poor concentration, and poor academic achievement--and that programs be created to improve sleep and mental health in adolescents with allergic disease.