Non-allergic rhinitis happens when the lining of the inside of the nose becomes swollen and inflamed, usually because of swollen blood vessels and fluid building up in the tissues of the nose.
This swelling blocks the nasal passages and stimulates the mucus glands in the nose, resulting in the typical symptoms of a blocked or runny nose.
Some of the main causes of non-allergic rhinitis include:
- environmental triggers
- medicines and recreational drugs
- overuse of nasal decongestants
- hormone imbalance
- nasal tissue damage
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.
In some people, rhinitis develops as a result of environmental triggers, such as:
The exact cause of this type of rhinitis is unknown, but it's most likely to happen in people with very sensitive nasal blood vessels.
Rhinitis can sometimes happen as a result of using certain medicines, including:
- angiotensin-converting enzyme (ACE) inhibitors – for high blood pressure
- beta-blockers – for various heart conditions
- non-steroidal anti-inflammatory drugs (NSAIDs) – to relieve pain
- nasal decongestant sprays
Rhinitis can also happen as a result of drug misuse (such as snorting 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 5 to 7 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.
Hormones may 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:
Various health conditions that cause a hormone imbalance in the body, such as an underactive thyroid gland (hypothyroidism), can also cause rhinitis.
Inside your nose, there are 3 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 happen 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.