Answer:

Nasal congestion occurs when airflow through the nose is obstructed, making it difficult for individuals to breathe through their nose and forcing them to breathe through their mouth.

Inside the nasal cavity are turbinates; the inferior turbinates contain erectile tissue that can expand and contract, controlled by the autonomic nervous system to regulate blood flow.

Normally, both sides of the nose do not ventilate equally at the same time. Every few hours, the erectile tissue in one turbinate expands, becoming slightly engorged and reducing airflow. Meanwhile, the opposite side contracts, allowing better airflow. After some time, the roles switch. This mechanism allows the nasal lining to "rest" alternately, preventing dryness and irritation from continuous breathing day and night. This is a normal physiological phenomenon, known as the nasal cycle, and is not a disease.

When lying on your side, the lower side of the head and nose (pressed against the pillow) is affected by gravity on the venous system that drains blood back to the heart. Blood vessels dilate, and the turbinates swell more, causing noticeable congestion on that side. Conversely, the upper nostril, not compressed, will be clearer. This explains why lying on your right side can lead to more congestion in the right nostril, and vice versa. Lying on your back often helps reduce congestion because pressure is distributed evenly across both sides.

When lying on your side, mucus has difficulty draining down the throat as it would in an upright position and tends to accumulate in the nasal lining. During sleep, the swallowing reflex also diminishes, contributing to greater mucus stagnation on the side you are lying on, making the sensation of congestion more pronounced.

Doctor Phat consults with a patient. Photo: Tam Anh General Hospital

Nasal congestion symptoms can stem from physiological or pathological causes. Congestion that occurs when changing sleeping positions, without accompanying headache, facial pain, reduced sense of smell, or bleeding, is physiological and does not require treatment.

If one-sided nasal congestion is constant, does not switch sides even with a change in position, lasts longer than two weeks, and is accompanied by yellow or green nasal discharge causing facial pain, a reduced sense of smell, or severe congestion after continuous use of nasal sprays, individuals should seek medical attention as these are signs of a pathological condition.

Some conditions that cause these symptoms include: the common cold, pharyngitis, allergic rhinitis, rhinosinusitis, structural abnormalities of the nose such as a deviated septum, turbinate hypertrophy, sinonasal tumors, foreign bodies, or enlarged adenoids.

If you experience nasal congestion with any of the aforementioned abnormal signs, you should consult an ear, nose, and throat specialist for a sinonasal endoscopy to accurately determine the cause and receive timely treatment.

Master, Doctor, Specialist Level I Truong Tan Phat

Head of Ear, Nose, and Throat Department

Tam Anh General Clinic, District 7