1. Sinusitis (Sinus Infection) Slideshow Pictures
2. Nasal Allergy Relief Products Slideshow Pictures
3. 10 Common Allergy Triggers Slideshow Pictures

Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Sinus infection facts
• What is a sinus?
• What is a sinus infection?
• What causes sinus infections?
• What are the types of sinusitis?
• What are the signs and symptoms of sinus infection?
• How is sinus infection diagnosed?
• How is sinus infection treated?
• Are there home remedies for a sinus infection?
• What are complications of sinus infection?
• Can sinus infection be prevented?
• Pictures of Sinusitis (Sinus Infection) - Slideshow
• Pictures of Nasal Allergy Relief Products - Slideshow
• Pictures of 10 Common Allergy Triggers - Slideshow
• Patient Comments: Sinus Infection - Symptoms
• Patient Comments: Sinus Infection - Causes
• Patient Comments: Sinus Infection - Home Remedies
• Patient Comments: Sinus Infection - Complications
• Patient Comments: Sinus Infection - Effective Treatments
• Find a local Ear, Nose, & Throat Doctor in your town
• Sinusitis Index

A sinus is a hollow, air-filled cavity. For the purposes of this article, a sinus will referred to those hollow cavities that are in the skull and connected to the nasal airway by a narrow hole in the bone (ostium). Normally all are open to the nasal airway through an ostium. Humans have four pair of these cavities each referred to as the:

1. frontal sinus (in forehead),
2. maxillary sinus (behind cheeks),
3. ethmoid sinus (between the eyes), and
4. sphenoid sinus (deep behind the ethmoids).

The four pair of sinuses are often described as a unit and termed the "paranasal sinuses." The cells of the inner lining of each sinus are mucus-secreting cells, epithelial cells and some cells that are part of the immune system (macrophages, lymphocytes, and eosinophils).

Functions of the sinuses include humidifying and warming inspired air, insulation of surrounding structures (eyes, nerves), increasing voice resonance, and as buffers against facial trauma. The sinuses decrease the weight of the skull.

Picture of the anatomy of the sinuses

Picture of the detail of the sinuses

A sinus infection occurs when a pathogenic microorganism (virus, bacterium, or a fungus) grows within a sinus and causes intermittent blockage of the sinus ostium. Drainage of mucus and pus often occur when the blockage is relieved. The drainage usually goes from the nasal passages to the throat or out the nostrils. Such infections also cause inflammation (an influx of immune cells and swelling of the sinus tissue) of one or more sinuses. This can to block the openings of the sinuses and leads to discomfort.

Inflammation of the air cavities within the passages of the nose (paranasal sinuses) is referred to as sinusitis. Sinusitis can be caused by infection, but can also be caused by allergy and irritation of the sinuses.

Sinusitis is one of the more common conditions that can afflict people throughout their lives. Sinusitis commonly occurs when environmental pollens irritate the nasal passages, such as with hay fever. Sinusitis can also result from irritants, such as chemicals or the use and/or abuse of over-the-counter (OTC) nasal sprays, and illegal substances that may be snorted through the nose. About 30 million adults have "sinusitis."

2011 was a year that sinus infections are getting much lay press as sinus infections have been reported in several sports figures in basketball and baseball. The sinus infections have been reported to alter the ability of the athletes to play at their peak performance. One young (18yr old) professional baseball player reportedly died from a bacterial sinus infection that spread to his brain. Also, about 15 trauma victims of the May 2011 tornado disaster in Joplin, Missouri developed fungal infections that are rarely seen (some of them in the sinuses).