Catarrh is usually caused by your immune system reacting to an infection, allergy, or irritation in your nose, sinuses, or throat, which makes the lining swell and produce extra mucus.

Quick Scoop: What causes catarrh?

Think of catarrh as your body “overreacting” with mucus when something bothers the lining of your airways.

1. Infections (very common)

These are the classic triggers, especially in colder months:

  • Common cold and flu.
  • Sinus infections (sinusitis).
  • Other viral upper respiratory infections.

When you catch a virus, the lining of your nose and throat becomes inflamed and starts producing more mucus than usual, which can drip down the back of your throat (postnasal drip).

2. Allergies and hay fever

Allergies are another major cause of catarrh.

  • Hay fever (pollen allergy).
  • Dust mite allergy.
  • Pet dander (cats, dogs).
  • Mold spores.

In these cases, your immune system treats harmless particles as threats, triggering swelling and extra mucus.

3. Non‑allergic rhinitis and irritants

Sometimes catarrh happens even when tests show no allergy.

Common non‑allergic triggers include:

  • Changes in weather or temperature (cold air, sudden humidity changes).
  • Strong smells, fumes, cleaning products, perfumes.
  • Cigarette smoke and air pollution or smog.

These irritate the nasal lining and can cause swelling and mucus without an immune “allergy” reaction.

4. Nose and sinus structure problems

Anything that affects normal drainage can lead to persistent catarrh.

  • Nasal polyps (small growths inside the nose or sinuses).
  • Deviated septum (the wall between your nostrils is crooked).
  • Other structural abnormalities in the nose or sinuses.

These can trap mucus, making you feel constantly blocked or “full” in the head.

5. Gastro‑oesophageal reflux (acid coming up)

Stomach acid rising up into the throat (GER or GERD) can:

  • Irritate the back of the throat and nose.
  • Trigger inflammation and an ongoing feeling of mucus.
  • Cause a catarrh‑type cough or constant throat‑clearing.

This is more likely if you notice heartburn, sour taste, or symptoms worse after meals or lying down.

6. Hormone changes

Hormones can subtly change how much mucus your body makes and how swollen your nasal lining feels.

  • Pregnancy.
  • Puberty.
  • Oral contraceptive (the pill) use.

These changes can sometimes lead to new or worse catarrh, even in people who have never had allergies before.

7. Food‑related triggers (especially spicy)

Certain foods don’t “cause” catarrh in a dangerous way but can temporarily increase mucus or make you notice it more.

  • Spicy foods (like chili, curry, hot sauces).
  • Foods you are allergic or sensitive to (for example, some people with food allergies notice more mucus after eating those foods).

This type of catarrh is usually short‑lived and settles once the trigger is gone.

8. Chronic catarrh and “sensitivity” to mucus

In some people, especially with long‑term catarrh, tests do not show clear infection or allergy.

  • The nerves that sense mucus in the back of the nose and throat may be unusually sensitive, so normal amounts of mucus feel like “too much.”
  • The brain may misinterpret these sensations, leading to constant awareness of mucus or the urge to clear the throat.

This is why some people feel blocked even when their nose actually looks clear on examination.

9. Stress and psychological factors

Stress and anxiety do not directly create mucus, but they can:

  • Increase muscle tension in the face, neck, and throat.
  • Change breathing patterns (more mouth breathing, shallow breathing).
  • Make you more aware of bodily sensations, including mucus.

All this can make catarrh feel worse or more constant.

At‑a‑glance causes (HTML table)

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Cause category Examples How it leads to catarrh
Infections Common cold, flu, sinusitis Inflame the nose and throat lining, causing swelling and excess mucus.
Allergies Pollen, dust mites, pet dander Immune system overreacts to allergens, triggering runny nose and postnasal drip.
Non‑allergic triggers Weather change, smoke, fumes, pollution Irritate nasal lining without allergy; cause swelling and mucus.
Structural issues Nasal polyps, deviated septum Block normal drainage, so mucus builds up and feels stuck.
Reflux (GER/GERD) Stomach acid reaching throat Irritates back of throat and nose, leading to chronic throat‑clearing and mucus sensation.
Hormonal changes Pregnancy, puberty, contraceptive pill Change blood flow and swelling in nasal lining, increasing congestion and mucus.
Food and drink Spicy foods, sometimes specific trigger foods Temporarily increase mucus production or trigger reflux.
Chronic sensitivity Heightened nerve response to mucus Normal mucus feels excessive; constant awareness of throat and nose.
Stress & anxiety Emotional strain, prolonged stress Increase muscle tension and symptom awareness, worsening the feeling of catarrh.

Mini “story” example

Imagine someone who gets a mild cold in January, then never quite feels clear again. The virus inflames their nose and sinuses, then spring arrives and pollen triggers hay fever on top of that. They start breathing more through their mouth at night, reflux worsens a bit, and now they wake with a dry throat and thick mucus every morning. By summer, the original infection is gone, but their nerves are so tuned in to every drop of mucus that the “catarrh” feels constant. This mix of infection, allergy, reflux, and sensitivity is very typical in chronic catarrh.

When to see a doctor

You should get medical advice if:

  • Catarrh lasts more than a few weeks with no clear cause.
  • You have severe facial pain, high fever, or very bad headache.
  • You notice blood in mucus regularly.
  • You have trouble breathing, swallowing, or unexplained weight loss.

A professional can check for infections, allergies, structural problems, or reflux and guide proper treatment.

Information gathered from public forums or data available on the internet and portrayed here.