The sinuses are hollow spaces in between the eyes, behind our cheekbones, and inside the forehead. They produce mucus to keep the nasal cavities moist and prevent dust particles from going into the lungs. They also help reduce the weight of the head.

Sinus infections occur when drainage of sinuses are blocked. In the previous post we had seen what is called sinusitis and what are its symptoms. We shall discuss the risk factors and causes of sinus infection in this post. The causes of sinus infection include environmental, physiological, and pathological ones.


Anyone can acquire a sinus infection. But certain risk factors and health conditions, such as the ones listed below, can increase your risk of developing one.

  1. Smoking
  2. Pollution and dust
  3. Allergies
  4. Nasal polyps
  5. Repeated nasal infections
  6. Systemic diseases
  7. Immune deficiencies
  8. Congenital disorders
  9. Structural abnormalities in the nose
  10. Dental infection
  11. Dehydration and cold air
  12. Nutritional deficiencies
Flower pollen triggers sinus infection
Man in a garden

The above three agents primarily dry up nasal secretions. The nasal surfaces are covered by a thin layer of fluid mucus that moves towards the throat. The mucus layer adds moisture to the inhaled air and has an antiseptic function. Smoking and polluted air deposit grit and soot particles on the mucus, making it viscous. The harmful gases from industrial and vehicular exhausts change the character of fluidic mucus causing the same effect. All three agents prevent the drainage of mucus from the sinuses producing stagnation. Consequently, bacteria and viruses grow and infect.

Exhaust from nuclear power plant causing air pollution
Exhaust from nuclear power plant
Air pollution by industries causes sinus infection
Exhaust from industries

The important aeroallergens include house dust mites, molds, pollens, and animal dander. Attacks of allergy disrupt the normal physiological function of mucus. Excessive runny nose during an allergy causes pent up secretions inside the sinus cavities. In addition to that, the swelling of the sino-nasal tract obstructs the outflow of mucus. Together, both result in sinusitis. The polyps are an aftereffect of repeated allergies and aggravate sinusitis. But, we shall discuss polyps in another post.


Patients with immune deficiencies, cancer, and diabetic mellitus suffer from repeated nasal infections and each infection takes a protracted course before settling down. Sometimes even healthy individuals and children have repeated nasal infections. These infections increase the risk of developing sinusitis. Reduced immunity seen in the above conditions hampers the strength of the body to fight against infections.


Congenital disorders are defects occurring in fetal development. Some such disorders result in thick mucus due to some fault in the production pathway. These disorders include cystic fibrosis, Young’s syndrome, and Kartagener’s syndrome. The latter two show repeated upper respiratory tract infections with infertility.


The deviated nasal septum is the most common structural problem producing obstruction to air and mucus flow. Often the ENT specialist suggests septal correction in addition to sinus surgery for optimum relief. Other abnormalities in the structure include an extra sinus cavity, narrow nose, enlarged turbinates, and convoluted sinus outflow tracts.


The roots of your molar teeth are very close to the floor of the maxillary sinus. We have had many cases when the tooth has gotten impacted inside the maxillary sinus. Poor oral hygiene, dental caries, and dental infections can produce sinusitis due to the close relationship between teeth and sinuses.


The cold air which blows out of the air-conditioner or that which is seen during the winter season dries up the mucus. Therefore, sinus infections are commoner in winters and in those who use AC daily. Adequate hydration is extremely important to maintain the fluid character of mucus and add moisture to the air we breathe.


The deficiency of Vitamin D is known to cause recurrent infections. Many studies have recently demonstrated how correction of this prevents sinus infections. Other vitamins of importance are B-Complex, Vitamin C, and Vitamin E.


The above list of risk factors constitutes the environmental and physiological causes of sinus infection. Although the above factors contribute, ultimately it is micro-organisms that invade the pent up secretions and produce the infection. The common organisms involved include bacteria, viruses, and fungi. Viruses are the most common, causing about 70-90% of the cases. Secondly, we have bacteria. A bacterial sinus infection requires antibiotics. Lastly, fungi produce about 5% of sinus infections. Certain fungi result in an indolent course of the disease but a few others cause a catastrophic end result. The latter type if seen in immune-deficient and diabetic patients.

Long-standing sinusitis and immune system abnormalities make the bacteria form a functional syncytium. We call it a biofilm in medical parlance. A biofilm has different groups of bacteria involved in specific activities that help the entity thrive despite antibiotics. It is very difficult to eradicate.

It is vital to diagnose the cause of sinus infection before instituting treatment. The factors which influence the mode of treatment, the investigations asked by an ENT, and the different modes of treatment for a sinus infection (or chronic sinusitis) are dealt with in the next post.

  1. Role of Vitamin D in Pathogenesis of Chronic Sinusitis With Nasal Polyposis
  2. Suffering from Sinus Problem? Air Pollution Could Be a Trigger
  3. Young Syndrome – A Rare Disease

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.