Causes of non-allergic rhinitis

Non-allergic rhinitis occurs when the lining of the inside of the nose becomes swollen and inflamed, usually because ofswollen blood vessels and fluid building upin the tissues of the nose.

This swelling blocks the nasal passages and stimulates the mucus glands in thenose, resulting in the typical symptoms ofa blocked or runnynose.

Some of the main causes of non-allergic rhinitis are described below.

Infection

In many cases, rhinitis develops as the result of an infection attacking the lining of the nose and throat.

This is usually a viral infection, such as a Cold , but bacterial or fungal infections can occasionally cause rhinitis.

Environmental triggers

In some people, rhinitis appears to develop as a result of environmental triggers, such as:

• smoke
• perfume
• paint fumes
• changes in the weather, such as a drop in temperature
• alcohol
• spicy food
• stress

The medical term for rhinitis caused by environmental triggers is vasomotor or autonomic rhinitis. The exact cause of this type of rhinitis is unknown, but it's believed to occur in people with very sensitive nasal blood vessels.

Medications and drugs

Rhinitis can sometimes occur as a result of using certain medications, including:

• angiotensin-converting enzyme (ACE) inhibitors a type of medication used to treat high blood pressure
• beta-blockers a type of medication used to treat various heart conditions
• non-steroidal anti-inflammatory drugs (NSAIDs) a type of medication commonly used to relieve pain
• nasal decongestant sprays (see below)

Rhinitis can also occur as a result of drug misuse (such as cocaine).

Overuse of nasal decongestants

Nasal decongestant sprays work by reducing the swelling of the blood vessels in your nose.

However, if they're used for longer than five to seven days at a time, they can cause the lining of your nose to swell up again. This can happen even after the cold or allergy that originally caused the problem has passed.

If you use more decongestants in an attempt to reduce the swelling, it's likely to make the problem worse.

The medical term for rhinitis caused by the overuse of nasal decongestants is rhinitis medicamentosa.

Hormonal imbalance

It's thought that hormones play a role in the enlargement of the nasal blood vessels that can lead to rhinitis.

Non-allergic rhinitis can also be caused by hormonal changes due to:

• pregnancy
• puberty
• taking hormone medication such as hormone replacement therapy (HRT) or the contraceptive pill

Various conditions that cause a hormone imbalance in the body, such as an underactive thyroid gland (hypothyroidism) , can also cause rhinitis.

Tissue damage

Inside your nose, there are three ridges of bone covered by a layer of tissue. These layers of tissue are called turbinates. A type of rhinitis called atrophic rhinitis can occur if the turbinates become damaged.

Most cases of atrophic rhinitis in the UK occur when the turbinates are damaged or removed during surgery (sometimes it's necessary to surgically remove turbinates if they're obstructing your airflow).

Turbinates play an important role in the functioning of your nose, such as keeping the inside of your nose moist and protecting the body from being infected with bacteria. If they're damaged or removed, the remaining tissue can become inflamed, crusty, and prone to infection.