What causes sinusitis infection?

Updated: Nov 18

Dr. K. R. Meghanadh


Sinusitis causes or etiology of sinusitis is multifactorial, i.e., multiple factors cause sinusitis.


Sinusitis infection causes

The cause of a sinusitis infection is the stagnation of water or fluids in the sinuses. Bacteria can grow in stagnant fluids in the outside environment or our bodies. This bacteria in stagnated water causes infection of the sinus's skin lining, causing sinusitis.


Role of the common cold

Most sinus infections can start as a routine viral infection, like a simple common cold that affects the nose and the structures in the nose. This causes swelling in the structures of the nose. Generally, this viral infection should subside in 5 to 7 days. If the patient has any of the below three conditions, this simple viral infection can provoke fluid stagnation, leading to sinusitis.


  1. Allergy

  2. Anomalies in the sinus drainage pathway

  3. Lesser immunity against bacteria by birth


Underlying conditions responsible for Sinusitis


1. Allergy

Allergy is one of the most common sinusitis causes.

Allergy increases mucin or fluid production more than required in the sinuses.


Sinuses are air-filled cavities with an opening for air entry, and mucin is produced in these sinuses to wash out unwanted external substances like dust, bacteria, and fungi. If a person has an allergy, mucin production increases abnormally due to an allergen.

What causes sinusitis infection? -  allergy, anatomy of sinus openings and pathways and immunity

Allergens are non-living objects that don’t multiply. They induce specific chemical reactions on the body and more so on the surface they contact, like the skin, the skin of the nose (nasal mucosa), lung mucosa, or eye mucosa. This mechanism helps your body to save from external agents.


In case of allergy, our body gives a hyper reaction. In the common tongue, we can say our body overreacts.


Examples of Allergy
  1. If dust enters your nose, you end up sneezing, or your nose secretes fluids. This process keeps your nose clean. In case of allergy: The sneezes could occur multiple times, even after dust removal. If the nose is secreting fluids instead of X ml of liquid to remove the allergen, it can produce 10X to 100Xml of fluid.

  2. When an insect contacts your skin before it bites, you will throw it out before it bites or causes harm. In case of allergy: An allergy doesn’t stop with simple itching. A rash is formed on the skin called Urticaria.


So, in an allergy patient, excess fluids are secreted by sinus walls that cannot come from the regular sinus openings. These extra fluids stagnate when a person has a viral infection that affects the nose.


2. Anomalies of the sinus opening and drainage paths


When the sinus’s openings and drainage path responsible for draining fluids out of the sinuses are compromised during a viral infection like the common cold, the additional swelling can cause stagnation of fluids resulting in infection of the sinus walls.


3. Lesser immunity against bacteria by birth

Some people have 5 to 10% lesser immunity against bacteria than average. Having lower immunity than a normal person can be one of the sinusitis causes.


An article by

Dr. K. R. Meghanadh

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