Sinusitis is the inflammation or swelling of the tissue lining the sinuses — the small air-filled spaces behind the forehead, cheeks, and eyes. When these passages become blocked with mucus, it can cause pressure, pain, and difficulty breathing through the nose. Sinusitis can be acute, lasting a few weeks, or chronic, lasting for months or recurring regularly throughout the year.

The condition often develops after a cold or respiratory infection when the sinuses become congested and bacteria or viruses grow in the trapped mucus. Common symptoms include facial pain or pressure, nasal congestion, thick nasal discharge, headache, and a reduced sense of smell or taste. Some people also experience toothache or ear pressure due to the buildup.

Allergies, nasal polyps, and structural issues such as a deviated septum can increase the risk of sinusitis. Environmental factors like pollution, cigarette smoke, and dry air can also irritate the sinuses, leading to inflammation. Identifying and managing these contributing factors can help prevent repeated infections.