Sinusitis, commonly known as a sinus infection, occurs when the bones and soft tissue in the sinuses become swollen, blocking sinus drainage and potentially causing an infection. Mucus, which is thick and sticky, plays a crucial role in trapping dust, bacteria, or other environmental irritants to prevent them from entering the body. This natural defense mechanism is vital whether the cause is a virus, the most common cause of sinus infection, or bacteria.

In adults, chronic sinusitis is often linked to nasal swelling caused by allergies, particularly to inhaled dust, mold, pollen, or fungal spores. These allergies trigger the release of histamine and other chemicals, leading to the inner lining of the nose swelling and blocking sinus drainage. Environmental factors, anatomical issues, and genetic predispositions can contribute to sinus blockage, but the primary cause is often swelling of the nasal passages due to common colds or allergies. Structural problems like a deviated septum can also lead to more severe sinusitis.

Symptoms of a sinus infection include painful pressure, bad breath, fever, lethargy, loss of smell or taste, and ear pressure. Sinus infection symptoms often start as a common cold and typically resolve within 7 to 10 days. However, other factors like cigarette smoke, changes in barometric pressure, nasal polyps, and a deviated nasal septum can also block sinuses and lead to infection.

Post-nasal drip can occur due to various reasons, including allergies, viral infections, sinus infections, and irritants in the air. Less common causes include foreign objects in the nose, pregnancy, and certain medications. In cases of sinusitis, inflammation of the sinuses and nasal passages can be relieved with several treatments. For more detailed information, visit Harvard Health, Chronic Sinusitis (in Adults) – Harvard Health, Nasal Allergies and Sinusitis – Harvard University, and What to do about sinusitis.