A sinus infection, also known as sinusitis, occurs when the cavities around the nasal passages become inflamed or swollen, often due to a viral infection, bacteria, or allergens. This inflammation can lead to symptoms such as nasal congestion, facial pain, and a thick nasal discharge. In some cases, a sinus infection can develop after a cold or other respiratory illness. Treatment for a sinus infection typically includes rest, hydration, and over-the-counter medications to relieve symptoms. In more severe cases, a healthcare provider may prescribe antibiotics if a bacterial infection is suspected. Most sinus infections resolve within a few weeks with proper care.