Sinuses are hollow cavities that are located in the skull. Sinuses differ in their size and location. The largest sinus is called the maxillary sinuses. Maxillary sinuses are located in the cheekbones. There is also a sinus located at the lower center of the forehead which is called the frontal sinus. The Ethmoid sinuses are located between the eyes, specifically at the nasal bridge. In a normal condition, sinuses are air filled cavities with a thin layer of mucous. Most sinuses drain into the nose through a small channel or pathway called the middle meatus.

However, in instances where the sinus becomes irritated and inflamed, the cavities get blocked which will then lead to congestion of mucous and air which will then result to sinus problems. Air which is trapped in the sinus cavities are the one which is responsible for the facial pains.

There are different types and cause of sinusitis. Virus is the most common causative factor of a sinus infection. There are also instances where your sinus inflammation is caused by other causative factors such as bacteria, allergen, and nasal deformities such as defects in the septum. Changes in temperature and humidity are another known factor that can trigger attack of a sinus infection. Swimming, diving, and cigarette smoking are also known to trigger the sinus infection attacks. When the sinuses are able to detect an invasion of foreign bodies, its natural immune response would be to increase mucous production. This accumulated mucous creates a friendly environment for bacteria and viruses to thrive in. The end result of this cycle will be inflamed sinuses leading to sinusitis. And the cycle goes on and on, unless the root cause is avoided and the symptoms are stopped.

Sinusitis can be categorized by duration and by location. If the infection will last less than four weeks, the infection is categorized as acute sinusitis. Acute sinusitis is often precipitated by a common upper respiratory tract infection. If the infection will last for more than six weeks and could last for a year or longer, then the condition is said to be chronic sinusitis. Symptoms of chronic sinusitis may include combination of any of the following: nasal congestion; pain in the facial area; headache; coughing during the night; an increase in previously minor or controlled asthma symptoms; general malaise; thick greenish or yellowish discharge; feeling of facial 'fullness' or 'tightness' which may worsen on bending over; dizziness, aching teeth, and/or halitosis or bad breath.

Categorizing sinusitis by location will depend on which sinus is infected. Paranasal sinuses comes in pairs, these includes the frontal, ethmoid, maxillary and sphenoid sinuses. The symptom will depend on which sinus pair is affected. For instance, Maxillary sinusitis causes pain or pressure in the maxillary or the cheek area examples are: toothache and headache. Frontal sinusitis can cause pain or pressure in the frontal sinuscavity which is located behind/above eyes. Ethmoid sinusitis can cause pain or pressure pain between/behindeyes. Lastly, sphenoid sinusitis can cause pain or pressure behind the eyes, but often refers to the vertex of the head.