The common cold is a frequently seen viral infectious disease of the upper respiratory system that affects the nose, sinuses, pharynx and larynx. It is caused by viruses, is self-limited and can affect people of all ages.

The main symptoms are: nasal congestion, runny nose and headache.

When a cold lasts more than 10 days, it is called acute post-viral rhinosinusitis. When the symptoms last more than 12 weeks (3 months), it is called chronic rhinosinusitis.

Rhinitis and sinusitis generally coexist and are concurrent in most individuals; therefore, the correct terminology is now rhinosinusitis. More of the expert panel guides and documents have now adopted the term rhinosinusitis instead of sinusitis.

Rhinosinusitis is defined as inflammation of the nose and sinuses characterised by two or more symptoms, one of which must be nasal blockage/obstruction/congestion or nasal discharge (anterior/posterior nasal drip), and there may also be:

• Facial pain/pressure reduction
• Loss of smell

• Acute: less than 12 weeks with complete resolution of the symptoms
• Chronic: lasting more than 12 weeks without complete resolution of the symptoms

Chronic rhinosinusitis may also be subject to exacerbations; on average, patients with chronic rhinosinusitis have 2.5 exacerbations per year.

The paranasal sinuses are 4 paired air-filled spaces that are found in the bones around the nose. The two frontal sinuses are located just above the eyebrows. The two maxillary sinuses are found in the cheekbones. The two ethmoidal sinuses are on each side of the nasal cavity. The two sphenoid sinuses are located behind the ethmoid sinuses.

Paranasal sinuses influence breathing, phonation, the heating and humidification of inspired air, and smell.

Normal paranasal sinus function depends on three essential components:

• Clear mucous secretions.
• Normal functioning of “microscopic hairs” (called “cilia”) that remove the mucus from the sinuses towards the nasopharynx.
• The opening of the holes (called sinus ostium) that communicate the sinuses with the ducts that lead the mucus towards the back of the nose (nasopharynx). These 3 components allow for the continuous discharge of mucous secretions from the sinuses to the nasopharynx.

The sinuses are mucus factories. People are always surprised to hear that the normal nose and sinuses produce approximately one litre of mucus every day! The mucus produced in the sinuses is driven by the microvilli (cilia) through the natural sinus openings (ostium) into the nasal cavity. This mucus layer helps purify, moisten and heat the inspired air. This mucus layer also traps particles such as bacteria and dust from the environment and is imperceptibly ingested every day. The acid found in the stomach destroys these trapped particles and bacteria.

Anything that interferes with one or more of these components that characterise normal sinuses may predispose patients to the development of rhinosinusitis. In other words, thick secretions, malfunctioning cilia or the blockage of sinus openings (ostiums) can cause sinusitis symptoms, such as nasal obstruction, runny nose, facial pain/pressure and other symptoms.