After the end of this large-scale infection, the investigators analyzed the re-diagnosis of patients with allergic rhinitis (AR) at the Otolaryngology Clinic, and found significant differences in symptoms between AR and non-AR patients. AR patients had more serious nasal and pharyngeal symptoms. In previous studies on the correlation between allergic diseases and COVID-19 infection, AR was found to be a protective factor to reduce COVID-19 infection and the risk of severe disease . In contrast, a cohort study in South Korea found that AR worsened COVID-19 infection . These studies mainly focussed on severe patients, and there was no comparison of symptom differences between AR patients and healthy people with mild infection.~Allergy may lead to the overall damage of nasal mucosa due to the mechanical and immune defense function of the virus. Immunotherapy will significantly reduce the number and severity of upper respiratory tract infections (including children's common cold). The investigators hypothesized that AR is more likely to aggravate symptoms after infection, while allergen immunotherapy （AIT） may reduce the risk of symptoms as a protective factor for symptoms after AR virus infection. Therefore, the investigators conducted a retrospective analysis on the risk of symptoms after COVID-19 infection in patients with AR, and compared the difference of symptoms after COVID-19 infection in patients with AIT and non-AIT AR.
At present, most studies mainly focussed on severe patients, and there was no comparison of symptom differences between AR patients and healthy people with mild infection to evaluate the symptoms of AR patients during infection and to provide preventive treatment in advance. So this experiment was designed.