A runny nose is very common and can happen for many different reasons. Sometimes the cause is obvious, such as a cold or allergies. Other times, especially when symptoms are persistent or mainly affect one side, it is worth looking more closely.
Common causes
A runny nose may be caused by:
- Allergies.
- Colds or viral infections.
- Non-allergic rhinitis, where the nose reacts to things like strong smells, temperature changes, smoke, or spicy food.
- Sinus inflammation or infection.
- Certain medications.
- Hormonal changes.
- Less commonly, a CSF leak, particularly when the fluid is very watery and comes mainly from one side.
What does the mucus look like?
The appearance of nasal mucus can sometimes give useful clues, but it does not always tell us the exact cause.
- Clear and watery mucus is common with allergies, viral infections, and non-allergic rhinitis.
- Thicker mucus can occur with inflammation or infection.
- Blood-stained mucus may happen from dryness, irritation, nosebleeds, or inflammation and should be assessed if it keeps happening.
When should you get it checked?
Consider an assessment if your runny nose:
- Lasts for several weeks.
- Keeps coming back.
- Is mainly from one side.
- Is associated with repeated nosebleeds.
- Comes with significant facial pain or pressure.
- Is associated with reduced smell.
- Is very watery and consistently comes from one nostril.
- Started after head injury or sinus/skull base surgery.
How is it evaluated?
The first step is understanding when the symptoms happen and what seems to trigger them.
A nasal examination may be enough in many cases. If needed, a small camera called a nasal endoscope can be used to look inside the nose.
Allergy testing, CT imaging, or other tests may be recommended depending on the pattern of symptoms.
How is it treated?
Treatment depends on the cause. It may include:
- Saline sprays or rinses.
- Steroid nasal sprays.
- Antihistamine sprays or tablets.
- Sprays specifically used for a watery runny nose.
- Avoiding triggers when possible.
- Treatment of underlying sinus disease or infection.
The most useful treatment depends on why the nose is running, rather than simply trying to dry it up.
Important: a very watery, persistent, one-sided runny nose is uncommon. In selected cases, especially after an injury or surgery, it may need to be checked for a CSF leak.