A sinus infection (sinusitis) can be caused by several factors:
Viral Infections: Most commonly, sinus infections are triggered by viruses, often following a cold or flu. The virus causes inflammation and swelling in the sinuses, leading to blocked passages and mucus buildup.
Bacterial Infections: If a viral infection leads to prolonged sinus congestion, bacteria can grow in the stagnant mucus, resulting in a bacterial sinus infection.
Allergies: Allergic reactions to pollen, dust, mold, or pet dander can cause inflammation in the sinus passages, making them more susceptible to infection.
Nasal Polyps: Noncancerous growths in the nasal passages or sinuses can obstruct airflow and mucus drainage, leading to infection.
Deviated Septum: A misaligned nasal septum can block normal sinus drainage, increasing the risk of infections.
Environmental Irritants: Exposure to pollutants, smoke, or chemicals can irritate the sinuses and increase the risk of infection.
Dental Infections: In rare cases, infections in the upper teeth can spread to the sinuses, particularly the maxillary sinuses.