Non-allergic rhinitis occurs when the nasal lining becomes swollen and inflamed, usually due to both swollen blood vessels and an accumulation of fluid in the tissues of the nose.
Blood vessels inside your nose help to control the flow of mucus by expanding and narrowing.
Swelling of the nasal lining causes congestion and stimulates the mucus glands in the nose, resulting in the typical symptoms of nasal obstruction, catarrh (a build up of fluid in the nasal cavities) and a runny nose.
There are several possible causes of non-allergic rhinitis described below.
Viral rhinitis
In cases of viral rhinitis, a virus attacks the lining of the nose and throat, resulting in it becoming inflamed and triggering the production of mucus.
Vasomotor rhinitis
For reasons that are unknown, people with vasomotor rhinitis have very sensitive nasal blood vessels. Environmental triggers can make the blood vessels expand, leading to congestion and a build-up of mucus. Common triggers include:
- chemical irritants, such as smoke, perfume or paint fumes
- changes in the weather, such as a drop in temperature
- alcohol
- spicy food
- stress
Atrophic rhinitis
Inside your nose, there are three ridges of bone covered by a layer of tissue. These layers of tissue are called turbinates. Atrophic rhinitis can occur if the turbinates becomes damaged.
Turbinates can be damaged by infection, although this is rare in the UK. Bacteria usually responsible for atrophic rhinitis, known as Klebsiella ozenae, are mainly found in India, China and Egypt.
In the UK, turbinates are more commonly damaged or removed during surgery. Sometimes it is necessary to surgically remove turbinates if they are obstructing your airflow.
Turbinates play an important role in the functioning of your nose by:
- keeping the inside of your nose moist
- protecting the body from being infected with bacteria
- regulating the air pressure of oxygen you breathe in
- containing important nerve endings that are used to transmit information, such as smells, to your brain
If a certain amount of turbinates are damaged or removed, the remaining tissue will become dry, crusty and prone to infection.
If you have atrophic rhinitis, you may also experience shortness of breath, because the turbinates are no longer able to regulate air pressure effectively and your lungs have to work harder to receive air. Many people also lose their sense of smell (anosmia).
The amount of turbinates that can be lost before atrophic rhinitis develops will differ from person to person. Some people lose a large amount of turbinates and never develop the condition, whereas others develop the condition after losing a small number of turbinates.
Rhinitis medicamentosa
Rhinitis medicamentosa is caused by the overuse of nasal decongestant sprays. It can also occur as a complication of cocaine misuse.
Nasal decongestants work by reducing the swelling of the blood vessels in your nose. However, if decongestant sprays are used for longer than 5-7 days at a time, they can cause the lining of your nose to swell up again, 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 is likely to make the problem worse. This is sometimes known as 'rebound congestion'.
It is possible to get locked into a cycle of overuse and dependence on nasal decongestants, in a similar way to becoming addicted to drugs.
Hormonal imbalance
Non-allergic rhinitis can also be caused by hormonal changes due to pregnancy, puberty or taking hormone replacement therapy (HRT) or the contraceptive pill. An underactive thyroid gland (hypothyroidism) is another possible cause.
It is thought that hormones play a role in the enlargement of the nasal blood vessels that can lead to rhinitis.
