This study aims to evaluate the effectiveness of hormone nasal drops in the olfactory cleft combined with olfactory training for treating postinfectious olfactory dysfunction (PIOD). The main questions this clinical trial seeks to answer are:

Can the combination of hormone nasal drops and olfactory training improve smell function better than olfactory training alone in PIOD patients? How does this combined treatment work?

Post-infectious olfactory dysfunction (PIOD) is a prevalent condition, particularly following viral upper respiratory infections such as COVID-19, and significantly impacts patients' quality of life. Current treatments primarily rely on olfactory training, but its effectiveness varies, with improvement rates ranging between 30% and 50%. Emerging evidence suggests that olfactory cleft obstruction and chronic inflammation play critical roles in PIOD pathogenesis, highlighting the potential benefits of targeted steroid therapy to address these underlying mechanisms.

In this study, the investigators planned to recruit 100 patients and divided them into two groups for combined therapy with steroid drops or placebo drops alongside olfactory training, and validate the effectiveness of the combined therapy based on the comparison of the outcomes of the two groups.

Inclusion Criteria:

1. Prospective enrollment of otolaryngology clinic patients aged 18-65 years with olfactory dysfunction. Diagnosis of post-infectious olfactory dysfunction (PIOD) will be based on the PPOD 2023 criteria. Participants must demonstrate olfactory impairment via Sniffin' Sticks testing, with TDI scores (sum of Threshold, Discrimination, and Identification) meeting: (1) Hyposmia: 16 < TDI < 30.75; (2) Anosmia: TDI ≤ 15.
2. Willingness to participate and signed informed consent.

Exclusion Criteria:

1. Use of systemic corticosteroids within 4 weeks or intranasal steroids within 2 weeks prior to enrollment.
2. Severe nasal septum deviation, nasal tumors, acute upper respiratory infections, or uncontrolled allergic rhinitis.
3. History of functional endoscopic sinus surgery or other nasal procedures within 12 months.
4. Severe cardiovascular disease, hepatic/renal insufficiency, uncontrolled diabetes, or immune system disorders.
5. Current or planned pregnancy.
6. Investigator-determined inability to comply with study requirements (e.g., memory/behavioral disorders, depression, heavy alcohol use, prior non-compliance).

We will decide whether to share the individual participant data after the study.