Allergic Fungal Sinusitis: Causes and Treatment Options

Do you often feel as though your nose is constantly blocked, no matter how many sprays, rinses or tablets you try? While sinus problems are common, there is one lesser-known subtype that often behaves very differently and tends to require more specialised care: allergic fungal sinusitis.

Unlike typical sinus infections caused by bacteria or viruses, allergic fungal sinusitis (AFS) develops when your immune system overreacts to airborne fungi. This response leads to ongoing inflammation, thick fungal mucus and nasal polyps that obstruct normal sinus drainage. Because of its chronic nature, allergic fungal sinusitis can be more persistent and challenging to manage. In this article, we look at what allergic fungal sinusitis is, why it happens, how it is diagnosed and the treatment options available.

What Exactly Is AFS?

AFS is a chronic inflammatory condition of the sinuses driven by an allergic response to common airborne fungi or moulds.

When fungal spores are inhaled, most people clear them without issue. In some individuals, however, the immune system overreacts, leading to persistent inflammation within the sinus cavities. Over time, this response causes a build-up of thick, sticky mucus known as allergic mucin, along with significant nasal congestion and the formation of nasal polyps. AFS is considered the most common form of non-invasive fungal sinus disease and is more frequently seen in people with underlying allergies or asthma.

What Factors Increase the Risk of AFS?

Although sensitivity to airborne fungi is the underlying driver of AFS, several factors can increase the likelihood of developing the condition or worsen its severity.

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• Frequent Exposure to Mould or Fungi

  : Regular inhalation of high doses of airborne fungal spores (like Aspergillus or Curvularia) increases the potential allergen load entering the nasal and sinus passages.

• Existing Allergies or Asthma

  :Individuals with allergic rhinitis or asthma have immune systems already prone to hypersensitivity, making them more likely to develop an exaggerated reaction to fungi.

• Chronic Sinus Inflammation

  :Persistent inflammation or infections, regardless of the initial cause, create an ideal, stagnant environment within the sinuses that promotes fungal survival and growth.

• Structural Sinus Abnormalities

  :Conditions such as a deviated septum or large nasal polyps physically obstruct natural sinus drainage, preventing the essential clearance of mucus, spores and debris.

• High Humidity and Poor Air Quality

  : Living or working in warm, moist climates or environments with poor air circulation promotes the abundant growth and concentration of the fungal spores that trigger AFS.

What Are the Symptoms of AFS?

AFS often causes symptoms that linger despite standard treatments. These signs may gradually worsen over time rather than resolving completely.

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• Nasal Congestion or Blockage

  : This is one of the most consistent symptoms and often does not improve with typical sinus medications. Blockage may be severe and long-lasting.

• Thick, Discoloured Nasal Discharge

  :Mucus is often thick, sticky and may appear yellowish or dark due to the presence of fungal material mixed with inflammatory debris.

• Facial Pressure or Pain

  :Inflammation within the sinuses can lead to a sensation of heaviness or aching across the cheeks, forehead or between the eyes.

• Decreased Sense of Smell

  : Swelling and obstruction in the nasal passages can significantly reduce the sense of smell, and in some cases, cause a temporary loss.

• Nasal Polyps

  :Soft, noncancerous growths commonly develop in the nose or sinuses. These polyps contribute to blockage and worsening congestion.

• Postnasal Drip

  : Excess mucus may drain down the back of the throat, leading to irritation, coughing or a constant need to clear the throat.

When Should You See a Doctor for Sinusitis in Singapore?

When sinus symptoms linger for weeks, worsen over time or keep returning despite home remedies or over-the-counter treatments, it may be a sign that something more persistent is going on. Ongoing issues like these can point to chronic sinus disease or a more complex underlying cause.

At this stage, seeing an ENT specialist becomes particularly important. Symptoms such as prolonged nasal blockage, facial discomfort, thick discharge or a reduced sense of smell should not be ignored. Early assessment allows for timely diagnosis and targeted treatment, helping to improve breathing, ease discomfort and reduce the risk of repeated infections.

How Is AFS Diagnosed?

Diagnosing AFS involves identifying both fungal material and evidence of an allergic reaction within the sinuses. Several tests may be used to confirm the condition:

• CT Scan

  A CT scan provides detailed images of the sinus cavities, revealing areas of blockage, dense mucus containing fungal elements and characteristic changes in the sinus walls. These findings help guide both diagnosis and treatment planning.

• Endoscopy

  Using a thin, flexible tube with a camera, doctors can directly examine the nasal passages and sinus openings. This allows them to identify thick mucus, fungal debris and nasal polyps, and to collect samples for laboratory analysis if needed.

• Biopsy

  Tissue or mucus samples are examined under a microscope to look for fungal elements and allergic mucin. This step helps differentiate allergic fungal sinusitis from other fungal or bacterial sinus infections.

What Are the Treatment Options for AFS?

Managing AFS usually involves both surgical and medical treatments. The aim is to clear fungal material, reduce inflammation and lower the chance of recurrence. Treatment options may include:

• Endoscopic Sinus Surgery

  Endoscopic sinus surgery is commonly performed to clear fungal debris, allergic mucin and nasal polyps. By restoring sinus drainage and airflow, surgery also allows topical medications to reach the affected areas more effectively.

• Corticosteroid Therapy

  Steroids play a key role in controlling inflammation. Nasal steroid sprays are often used long term, while short courses of oral steroids may be prescribed during flare-ups or when polyps recur.

• Saline Nasal Irrigation

  Regular saline rinses help remove remaining mucus, debris and microscopic fungal particles. This simple at-home practice supports healing, reduces congestion and keeps the nasal passages moist.

• Antifungal Medications

  Topical or oral antifungal treatments may be considered in certain cases, especially when symptoms continue despite surgery and corticosteroid therapy. These medications are used selectively when there is ongoing evidence of fungal involvement.

Finding Long-term Relief from Sinus Symptoms

Living with constant nasal blockage, facial pressure or breathing difficulties can gradually take a toll on your daily comfort. When symptoms persist or keep returning, early diagnosis paired with personalised care not only helps relieve current discomfort but also lowers the risk of future flare-ups, supporting better sinus health in the long run.

Our sinus doctor, A/Prof Luke Tan, is an ENT surgeon in Singapore with experience in endoscopic sinus surgery, thyroid surgery and head and neck conditions. For care that is centred on your needs and focused on lasting relief, get in touch with us today to book a consultation.