Nasal congestion is a condition characterized by a feeling of blocked or stuffy nasal passages, typically caused by inflammation and swelling of the nasal tissues and increased mucus production. It commonly occurs with colds, sinus infections, allergies, or respiratory infections, but may also result from irritants such as smoke, strong odors, or environmental pollutants. Symptoms often include difficulty breathing through the nose, sinus pressure, headache, postnasal drip, and reduced sense of smell. Nasal congestion can be temporary and mild or persistent and disruptive, particularly when associated with chronic sinusitis or allergic rhinitis. Identifying the underlying cause is important for appropriate management and relief.