The common causes of unilateral nasal congestion mainly include abnormal nasal structure, nasal tumors, unilateral sinus infection, and nasal foreign bodies. 1. Abnormal nasal structure. For example, deviated nasal septum can cause unilateral narrowing of the nasal cavity, resulting in unilateral nasal congestion. 2. Nasal cavity tumor. Benign tumors such as inverted papilloma can cause unilateral nasal congestion. In addition, malignant tumors of nasal cavity, such as maxillary sinus malignant tumor, can cause unilateral nasal congestion. 3. Unilateral sinus infection. Chronic rhinitis is mainly manifested as alternating nasal congestion, chronic maxillary sinusitis and maxillary sinus posterior nostril polyp, can cause unilateral nasal congestion. 4. Nasal foreign body. Nasal foreign body is more common in children with unilateral nasal congestion, common foreign body has soybean, paper ball and so on. Others, such as nasopharyngeal lesions, such as adenoid hypertrophy, mostly bilateral nasal congestion, can also appear unilateral posterior nostril nasal congestion. Nasopharyngeal malignant tumors, such as squamous cell carcinoma, rarely cause nasal congestion, but unilateral nasal congestion can also occur. If unilateral nasal congestion occurs, one should consult a doctor to confirm the diagnosis in time and get timely treatment.