Introduction

Nasal congestion, or nasal obstruction, commonly known as stuffy nose, is a frequent health complaint that affects people of all ages.¹ It is a common condition where the nasal passage becomes swollen due to inflamed blood vessels which leads to problems in breathing. Often, it is dismissed but in chronic congestion, it may significantly hinder daily life, causing discomfort, difficulty in breathing, and disrupt sleep. Nasal congestion affects 10-30% of the global population due to allergic rhinitis and about 12% due to chronic rhinosinusitis, which is common with respiratory infections like the common cold.

The immune system plays an essential role as a defence mechanism in the body by protecting against harmful diseases caused by organisms or allergens. It does so by triggering inflammation and releasing chemicals to protect the body from threats.² 

Nasal congestion occurs when the immune system detects allergens or irritants that trigger inflammatory responses. Understanding this connection is, therefore, essential for effectively managing and preventing nasal congestion.

What is nasal congestion?

Nasal congestion is a condition characterised by mucus secretion and inflammation of nasal tissue. This can lead to a sensation of a blocked or stuffy nose, making it difficult to breathe normally.³

Sometimes nasal congestion is not a disease in itself but can be a symptom of another underlying issue. Common symptoms of nasal congestion include blocked or runny nose, difficulty breathing, and headaches.

Typical causes of nasal congestion include allergies, infections, and irritants:

• Allergies Rhinitis (hay fever) - Exposure to tiny allergens like pollen, dust mites and moulds can trigger an immune response, leading to inflammation and congestion.
• Non-allergic rhinitis includes
  1. Infections - both bacterial and viral infections which cause nasal congestion in response to the pathogens
  2. Environmental irritants which include smoke, pollution, and strong odours can irritate the nasal passages, causing inflammation and congestion⁴

The immune system and its functions

To understand the link between nasal congestion and the immune system, it is essential to have a basic understanding of how the immune system works. The immune system is a complex defence mechanism that protects the body against pathogens and maintains health.⁵ 

White blood cells- Also known as leukocytes, these are the primary defence mechanism against infection. They identify and target pathogens.

Antibodies-major proteins produced by the immune system and found in blood and on mucosal surfaces are essential for immunity.⁶  

The immune system is triggered by antigens, like proteins found in bacteria, viruses, and fungi, which bind to receptors on immune cells. When the body first encounters a germ, it learns how to fight it and stores that information. If the same germ appears again, the immune system recognises it and responds more quickly. The body's cells also have proteins on their surfaces, but they don't usually activate the immune system. However, in some cases, the immune system mistakenly attacks the body's healthy cells, causing an autoimmune response.² 

How the immune system causes nasal congestion

When the immune system detects a foreign substance- either allergen or pathogen- it triggers a complex immune response. This response is designed to protect the body, but it can also cause inflammation and other symptoms, including nasal congestion.

In allergic rhinitis, nasal congestion is caused by an immune response to allergens. When an allergen enters the nasal passage, it triggers the release of immunoglobulin E (IgE) in mast cells. This, in turn, leads to the release of substances like histamine and protease, which cause inflammation. Other inflammatory molecules like leukotriene, prostaglandins, and cytokines such as TNFa and IL-4 are also produced. Together, these cause swelling and fluid buildup in the nasal tissue, leading to congestion and other symptoms. 

Acute sinusitis, which is usually caused by a common cold, occurs when the body encounters a pathogen. The WBC read the site of infection, releasing chemical and other signalling molecules, causing blood vessels to expand and the nasal passage to swell. The body responds by increasing blood flow to the affected vessels, making them more permeable, which results in congestion as it tries to flush out the invaders. That's what makes your nose feel stuffy or runny during a cold or sinus infection.⁷

Chronic nasal congestion persists over weeks or even months due to ongoing exposure to allergens or repeated infections. In this state, the immune system remains alert, causing long-term inflammation and tissue damage in the nasal passage.

Common triggers of nasal congestion related to immune response

Several factors can trigger the immune system to cause nasal congestion. Some of these include: 

1. Allergic reactions (allergic rhinitis)- Allergic rhinitis or hay fever occurs when the immune system overreacts to allergens like pollen, mould spores, dust mites, or pet dander. Symptoms include sneezing, itching, running nose and congestion
2. Viral infection (common cold) or bacterial infection (sinusitis) are significant triggers for nasal congestion. The immune system recognises these pathogens and responds by releasing histamine and other chemical mediators of inflammation, causing congestion in the nasal passage
3. Environmental factors trigger non-allergic rhinitis, stimulating the immune system and directly irritating the nasal mucosa⁸

Managing nasal congestion by supporting the immune system

Effective management of nasal congestion along with symptoms and underlying immune response. Some management strategies include:

1. Medication: The most evaluated therapies for nasal congestion include antihistamines, corticosteroids, nasal decongestants, and leukotriene antagonists.
   • Antihistamines block the effects of histamines, reduce inflammation, and alleviate symptoms such as sneezing, itching, and congestion. They are also first-line therapy for allergic rhinitis. All H1 antihistamines have anti-inflammatory properties
   • Topical (intranasal) corticosteroids have proven effects in allergic rhinitis and nasal polyps by suppressing inflammation (pro-inflammatory cytokines as well as eosinophils and Th-2 cells. Mometasone, fluconasole, and ciclesonide help manage nasal congestion. However, it is only recommended for short-term use to prevent side effects like nasal tissue thinning 
   • Nasal decongestants, such as xylometazoline and oxymetazoline, can reduce nasal stuffiness by vasoconstriction(narrowing of swollen blood vessels). They may be beneficial in the treatment of rhinosinusitis symptoms but should only be used for 3–5 days to avoid side effects, such as rebound congestion or rhinitis medicamentosa, a condition where congestion worsens due to overuse. Systemic decongestants like pseudoepinephrine are available but may lead to side effects such as high blood pressure, insomnia and appetite loss
   • Other therapies, including antibiotics, treat acute bacterial infections in combination with nasal steroids. Leukotriene receptor antagonists like montelukast block allergic reactions. Immunotherapy and biological therapies, such as omalizumab, address severe allergies, while antibiotics treat bacterial infections, especially in chronic cases⁹

2. Lifestyle changes: Keeping a healthy diet is essential in boosting the immune health. These include antioxidant-rich fruits, vegetables, whole grains, and lean proteins that can help support the immune system. Hydration is another factor that helps with the thinning of mucus, making it easier to clear from the nasal passages and reducing congestion. Moreover, adequate rest is crucial for maintaining a healthy immune system. Aim for 7-9 hours of quality sleep per night to allow the body to repair and strengthen its defences.    
3. Natural remedies- Hypertonic intranasal saline irrigation has anti-inflammatory effects and helps in removing chemicals/ mediators of inflammation. It is recommended as it has minimal adverse events. When compared to an isotonic solution, a hypertonic solution helps in thinning and clearing mucus and preventing bacterial infection. Moreover, it also helps in symptomatic relief.¹⁰

Preventing nasal congestion through immune system health

• Strengthening the immune system and avoiding triggers play a key role in prevention, as well as reducing the severity of nasal congestion. Tips for boosting the immune system include keeping a rich diet with essential nutrients. Involve foods rich in vitamins (A, C, D, E) and minerals (zinc, selenium) for a robust immune system. Foods like citrus fruits, nuts, seeds, leafy greens, and fish can provide these nutrients¹¹ 
• Exercise- maintaining a healthy routine and regular physical activity improves blood circulation, relieves stress and enhances the immune system
• Strategies should be taken to avoid common allergens and irritants. These include minimising allergen exposure using air purifiers. Avoid exposure to smoke, pollution and strong odours and use hypoallergenic cleaning products and fragrances
• Staying up-to-date with vaccinations, like the flu shot, can help protect against common infections that cause nasal congestion

Summary 

Nasal congestion is more than just a minor annoyance; it is a sign that the immune system is actively working to protect the body. By understanding the link between nasal congestion and the immune system, you can take proactive steps to effectively manage and prevent symptoms. From using medications and natural remedies to making lifestyle changes and boosting immune health, there are many strategies to help you breathe easier and improve your quality of life. If your nasal congestion persists or is severe, consult a healthcare professional for personalised advice and treatment options.