1. Chronic use of nasal or systemic corticosteroids 2. History of smell loss before COVID-19 era 3. Previous history of rhinological diseases such as chronic rhinosinustis, nasal tumor, anatomical abnormalities of the nose 4. Pregnancy 5. The patients who refuse to enroll the study.

1. Chronic use of nasal or systemic corticosteroids 2. History of smell loss before COVID-19 era 3. Previous history of rhinological diseases such as chronic rhinosinustis, nasal tumor, anatomical abnormalities of the nose 4. Pregnancy 5. The patients who refuse to enroll the study.