Allergy, Nose & Sinus

Sinus and sinusitis – What is the difference?

January 25, 2024
Overview picture

Many people with nose symptoms often visit a doctor and say, “Doc, I have sinus”. The reality is, everyone has sinuses! They are part of the normal anatomy of a human face. In this article, Dr Gan explains the difference between sinus and sinusitis, as well as the causes, symptoms, diagnosis and treatment of sinusitis.



What are sinuses?


The precise medical term is paranasal sinuses. They are air-filled cavities surrounding the nasal cavity. Humans have four groups of sinuses within their face, on each side of their nasal cavity (Figure 1). They are located:


  1. Above the eyes (frontal sinus)
  2. In between the eyes (ethmoid sinus)
  3. Below the eyes (maxillary sinus)
  4. Behind the eyes (sphenoid sinus)


Sinus Chart

Figure 1 – Locations of the different sinuses surrounding the nasal cavity



The lining of the nose and sinuses (mucosa) produces mucous. The mucosa has very small hair-like structures that help move the mucous from the sinuses into the nose. The mucous in the nose can then be blown out, swallowed into the stomach or coughed out as part of the phlegm.



What are the functions of the sinuses?


Why sinuses exist is largely unknown. However, as they are air-filled, they are thought to reduce the weight of the human head. Sinuses also produce mucous that traps inhaled bacteria and foreign objects, change the temperature of inhaled air and enhance the resonance of human voice.



What is sinusitis?


Sinusitis (or the preferred medical term of Rhinosinusitis) is the inflammation of the lining of the nose and sinuses. This is the condition that most people refer to when they walk into the clinic and say they have “sinus”. Sinusitis is further divided into “acute” and “chronic”, depending on the duration of the symptoms; if the symptoms are less than three months, the condition is “acute”, and if they are more than three months, the condition is “chronic”.



What causes sinusitis?


There are many causes of sinusitis. The sinuses become inflamed and infected when the drainage pathway is blocked. The stagnant mucous in the sinuses can get secondarily infected, resulting in the symptoms of sinusitis (Figure 2). The drainage pathways of the sinus can be naturally narrow in some patients (i.e. genetic). A deviated nasal septum (the bent central wall of bone and cartilage in the nose that divides the nasal cavity into right and left halves) can also block the sinus passage. This can occur as a result of trauma or is inborn in some patients.



Normal Sinusitis sinuses

Figure 2 – A comparison between sinusitis (infected sinus) and normal sinuses



In patients with severe allergic rhinitis (sensitive nose or hay fever), the congestion and swelling in the nose can cause rhinosinusitis. In some patients, sinusitis occurs because the lining of their nose and sinuses is ineffective in moving mucous out of the nose. If the patient has poor immune system, the risk of getting a sinus infection is also higher.



What are the symptoms of sinusitis?


Patients with sinusitis usually experience blocked nose, nasal congestion, coloured (usually yellow, brown or green) mucous which can drip forward (as a coloured nasal discharge) or backwards (as a postnasal drip), facial pain or fullness, and in some cases, a decreases or loss of smell. In acute sinusitis (less than 3 months duration) some patients may experience fever. Other associated symptoms include headache, ear pain and blockage, and fatigue. In chronic sinusitis (more than 3 months duration), the symptoms are similar. However, some patients with chronic sinusitis may have nasal polyps (soft painless non-cancerous growth) which are more difficult to treat and control.



How is sinusitis diagnosed?


Your ENT surgeon will review your symptoms and perform a thorough physical examination which may include a flexible nasoendoscopy (Figure 3). A nasoendoscopy (a flexible lighted tube with a camera attached to one end) is inserted into the nose and throat to look for signs of sinusitis. This can be done after the nose is numbed and decongested with a local anaesthetic spray. The process takes less than three minutes and most of the time is painless (with only a mild discomfort felt during the procedure). Some of the clinical findings of sinusitis include pus, swelling of the lining of the nose and polyps.



Figure 3- Flexible nasoendoscope is inserted in the nasal cavity and is guided to the posterior nasal space (back of nose) and to the level of the larynx (voice box)



How is sinusitis treated?


To treat sinusitis, the following medications may be prescribed:


  1. Antibiotics to treat the bacterial infection
  2. Nasal irrigation (salt solution) to wash out the mucous and pus
  3. Nasal steroid sprays to reduce inflammation of the sinonasal mucosa
  4. Mucolytics to facilitate removal of mucous
  5. Pain relievers to reduce headaches and facial pain
  6. Oral steroids in patients with nasal polyps


In majority of the cases, sinusitis can resolve with medical treatment. However, in some instances, sinusitis may persist or is recurrent despite maximal medical management. In such cases, a functional endoscopic sinus surgery (FESS) may be necessary and offers an excellent chance of improvement in symptoms. The surgery is minimally invasive (done through the nose) and aims to open up the blocked sinuses to facilitate ventilation and drainage of the sinuses (Figure 4).



Fess Figure

Figure 4- Functional Endoscopic Sinus Surgery (FESS) is indicated in patients with recurrent sinusitis or recalcitrant sinusitis that has failed maximal medical management



Best wishes,


Dr Gan Eng Cern
ENT Specialist Singapore

    When Should You See an ENT Specialist in Singapore?

    • Any ear, nose or throat symptoms that you are troubled with or concerned about
    • Persistent blocked nose with mouth breathing or snoring

    Dr Gan Eng Cern

    Dr Gan Eng Cern is a distinguished ENT doctor with fellowship training. In addition to his clinical practice as an ear, nose and throat specialist in Singapore, Dr. Gan has contributed to the academic field as a Senior Clinical Lecturer at the Yong Loo Lin School of Medicine, National University of Singapore. He is recognised for his extensive research work, with numerous contributions to reputable international ENT journals. Dr Gan is also highly sought after as a speaker and has shared his surgical knowledge as a surgical dissection teacher at various prominent ENT conferences and courses.


    • 2020 – Reader’s Choice Gold Award for Best ENT Specialist (Expat Living Singapore)
    • 2016 – Best Educator Award (Eastern Health Alliance)
    • 2016 – “Wow” Award (Patient Compliment)
    • 2014 – Eastern Health Alliance Caring Award – Silver
    • 2014 – 19th Yahya Cohen Memorial Lectureship (awarded by the College of Surgeons, Academy of Medicine Singapore for best scientific surgical paper)
    • 2012 – Human Manpower Development Award (Ministry of Health, Singapore)
    • 2007 – Singhealth Best Doctor Award


    • MBBS – Bachelor of Science, Bachelor of Medicine, Bachelor of Surgery (University of New South Wales, Sydney, Australia)
    • MRCS (Edin) – Member of the Royal College of Surgeons Edinburgh, United Kingdom
    • MMed (ORL) – Master of Medicine in ENT (National University of Singapore)
    • FAMS – Fellow of the Academy of Medicine Singapore

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