A sinus infection, which is also known as sinusitis, occurs when the normally air-filled sinus cavities becomes inflamed in a way that prevents the normal passage of mucus, according to MedlinePlus. The inflammation can be caused by a fungus, bacteria or virus.
In many cases, antibiotics are not needed for a sinus infection. According to the Centers for Disease Control and Prevention, only acute sinus infections caused by bacteria require the use of antibiotics. Most sinus infections are caused by a virus, so no antibiotic treatment is required. Sinusitis can also be caused by allergies, structural defects and pollutants. Treating the underlying issue can treat the sinus infection.