Catarrh is caused by the immune system reacting to an infection or irritation in an airway or a cavity of the body, such as inside the nose.

Your immune system sends infection-fighting white blood cells to the source of the infection.

The white blood cells cause the mucous membrane that lines the affected area to swell and produce mucus. The swelling will also narrow the cavity, resulting in further congestion.

Catarrh triggers

The most common triggers of catarrh are:

• infections, such as the common cold
• allergic reactions, such as reactions to pollen (hay fever) or dust mites (allergic rhinitis)

Other triggers include non-allergic rhinitis and nasal polyps.

Non-allergic rhinitis

Some people have abnormally sensitive blood vessels that react to environmental triggers, such as cigarette smoke and pollution. The reasons for this over-sensitivity are unknown.

The affected blood vessels become enlarged (swollen) in a similar way to their response to an infection or allergic reaction. The swelling leads to congestion and catarrh.

As well as cigarette smoke and pollution, other triggers of non-allergic rhinitis include:

• chemical irritants, such as perfume or paint fumes
• changes in the weather
• alcohol 
• spicy food
• stress 

Read more about non-allergic rhinitis.

Nasal polyps

Nasal polyps are non-cancerous, fleshy swellings that grow from the lining of your nose or your sinuses (the small cavities inside your nose).

The polyps can prevent mucus from properly draining out of your nose or sinuses, leading to congestion and catarrh.

Read more about nasal polyps.

In most cases, catarrh does not need to be diagnosed because the underlying infection will pass quickly, often without treatment.

Persistent catarrh

Further investigation will be required in cases where catarrh persists for longer (chronic catarrh).

Your GP may examine your nose to check for nasal polyps (fleshy swellings that develop in the lining of the nose that prevent mucus from draining properly).

Your GP may also want to check that your catarrh is not the result of an allergic reaction. You’ll be asked whether your symptoms are worse in particular environments or at certain times of the day or year. This will help them to pinpoint a possible allergen (a substance that causes an allergic reaction).

In rare cases, an allergy test may be recommended if an allergic reaction is thought to be causing your catarrh, and the allergen responsible is not known. This will usually involve having a skin prick test, where allergens are placed on your arm and introduced into your skin by pricking it with a short pin. If you are allergic to the substance, a small welt (itchy spot) will appear.

Read more about diagnosing allergic rhinitis.

Persistent catarrh can also be caused by non-allergic rhinitis. Diagnosing non-allergic rhinitis can be difficult because it shares many of the same symptoms as allergic rhinitis, but there are no specific tests for the condition.

If allergy tests reveal you are not experiencing an allergic reaction, non-allergic rhinitis may then be diagnosed.

Catarrh is an excessive build-up of thick phlegm or mucus in an airway or cavity of the body.

It is usually found in the sinuses (air-filled cavities in the bones of the face that drain into the nose), but it can also occur in the throat, ears or chest.

This can lead to:

• a blocked and stuffy nose
• a runny nose or mucus that runs down the back of your throat
• an irritating, persistent cough caused by excess mucus at the back of your throat
• a headache
• facial pain caused by a blocked nose and blocked sinuses
• a loss of smell and taste
• temporary, partial hearing loss and a crackling sensation in your middle ear
• tiredness

What causes catarrh?

Catarrh is caused by the immune system reacting to an infection or irritation. The immune system is the body’s natural defence against infection and illness.

Your immune system sends infection-fighting white blood cells to the source of the infection or irritation. These release molecules called inflammatory mediators which cause the mucous membranes to swell and produce mucus. The swelling also narrows the cavity, resulting in further congestion.

Catarrh is not a condition itself, but a symptom of conditions such as:

• the common cold or other infections
• hay fever or other types of allergic rhinitis – nasal inflammation caused by an allergic reaction to allergens such as pollen, animals or dust mites
• non-allergic rhinitis – sensitivity to environmental triggers, such as changes in humidity  
• nasal polyps – fleshy swellings inside the nose

The links above provide more detailed information on these conditions.

Chronic catarrh

In some cases, people can experience chronic catarrh, which is not caused by an allergy or infection and lasts for a long time. The cause of chronic catarrh is unknown but it may be related to an abnormality in the lining of the throat.

Should I see my GP?

In most cases, catarrh will clear up as the underlying infection only lasts a short period of time.

However, some people may experience chronic catarrh, which can be frustrating to live with.

If your catarrh persists, speak to your GP. They may want to rule out conditions such as nasal polyps and find out if your catarrh is being caused by an allergic reaction.

Self-help techniques are often the best way of managing chronic catarrh if a cause cannot be found.

Treating catarrh

If your catarrh hasn’t cleared up on its own, your treatment will depend on the underlying cause.

When no cause can be identified, self-help techniques are the best way to relieve symptoms. This may include:

• simple environmental changes – such as avoiding warm, dry atmospheres
• avoiding dehydration
• saline nasal rinses
• decongestant medicines

Read more about how catarrh is treated.

Treatment for catarrh may not be necessary because it often disappears within a few days, after your body has fought off the infection.

If treatment is required, the type of treatment recommended will depend on the underlying cause. For example:

• rhinitis can usually be managed by avoiding the allergens or environmental triggers that cause catarrh – read more about treating allergic rhinitis and treating non-allergic rhinitis
• nasal polyps may be treated with a nasal spray containing steroids, or surgery may be used to remove larger nasal polyps – read more about treating nasal polyps

Chronic catarrh

If no cause can be found, you may be able to reduce the amount of catarrh you produce with the following self-help techniques:

• avoid atmospheres which may dry out your airways – for example, air conditioning and car heating systems
• plants or bowls of water in a room may help to moisten the atmosphere
• ensure you are not dehydrated
• try to breathe through your nose instead of your mouth
• use a saline nasal rinse several times a day – these can be bought from a chemist or made at home with half a teaspoon of salt in a pint of boiled (then cooled) water
• decongestants (see below)

Decongestant medication

Decongestants help relieve a blocked nose by reducing swelling of blood vessels in your nose.

Decongestants are available in tablet form or as a nasal spray and can be bought from pharmacies without a prescription. Oral decongestants (those taken by mouth) may take a little longer to work, but their effect can last longer than nasal sprays.

You should not use decongestants for more than five to seven days at a time. This is because they only provide short-term relief and using them for longer than seven days may make your symptoms worse.

Decongestants do not usually cause side effects and, if they do, they are likely to be mild. Possible side effects of decongestant nasal sprays may include:

• irritation to the lining of your nose
• headaches 
• nausea (feeling sick)

Read more about decongestant medicines.