[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [ENT](https://durgical.com/en/ent/) › [Nose and sinuses: approach to complaints](https://durgical.com/en/ent/areas/nose/) › Approach to a runny nose, including CSF leak

# Approach to a runny nose, including CSF leak

- Approach to a complaint

Most runny noses are viral or allergic; clear, one-sided, persistent discharge means thinking of a cerebrospinal fluid leak.

Updated Nov 5, 2026

## Key points

- The common cold is viral: do not prescribe antibiotics.
- Bacterial rhinosinusitis: more than 10 days without improvement, severe onset or worsening after improvement.
- Watery discharge with sneezing and itching: allergic rhinitis; an intranasal corticosteroid is first line.
- Clear one-sided discharge after trauma or surgery: beta-2 transferrin to confirm CSF.
- One-sided foul discharge in a child: foreign body.

## What it is

Rhinorrhoea is almost always due to a viral cold or allergic rhinitis and does not need antibiotics. The approach separates infectious from allergic and non-allergic causes, and recognises bacterial rhinosinusitis by its course: it lasts more than 10 days without improving, is severe from the start or worsens after improving. One-sided discharge deserves special attention: in a child it is usually a foreign body, in an adult it may be a tumour, and if it is clear and watery, especially after trauma or surgery, it may be cerebrospinal fluid with a risk of meningitis.

## Key questions in the history

- One side or both? Clear, purulent or bloody?
- Since when? Did it improve and then worsen?
- Sneezing, itching, watery eyes, triggers such as dust or animals?
- Does it increase on leaning forward or taste salty? Head injury or nasal surgery?
- Worse with cold, smells or eating?
- Topical decongestant use?

## Causes and classification

- Infectious: viral common cold (the most frequent) and acute bacterial rhinosinusitis.
- Allergic: watery, with sneezing and nasal or eye itching; seasonal or perennial.
- Non-allergic: vasomotor (temperature changes, smells), gustatory (when eating) and rhinitis medicamentosa.
- One-sided: foreign body in a child, tumour in an adult, CSF leak.
- CSF leak: traumatic (skull base fracture, surgery) or spontaneous.

## Step-by-step approach

- Define whether it is one-sided or bilateral, clear or purulent, and its duration.
- Look for allergic or irritant triggers, a link with meals and decongestant use.
- Classify rhinosinusitis: viral if it improves before 10 days; bacterial if it persists, is severe or worsens after improving.
- If it is clear, one-sided and increases on leaning forward, or follows trauma or surgery, collect a sample for beta-2 transferrin.
- If it is one-sided, purulent and foul in a child, look for a foreign body.
- If it is one-sided with blood or blockage in an adult, arrange nasal endoscopy to rule out a tumour.

## Differential diagnosis of a runny nose

| Cause | Discharge | Key clue |
| --- | --- | --- |
| [Common cold](https://durgical.com/en/conditions/common-cold/) | Clear, later thicker | Early fever if any; self-limiting course |
| [Acute bacterial rhinosinusitis](https://durgical.com/en/conditions/acute-rhinosinusitis/) | Purulent | Over 10 days, severe or worse after improving |
| [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/) | Watery, bilateral | Sneezing, itching, conjunctivitis |
| Vasomotor or gustatory rhinitis | Watery | Cold, smells or meals; no itching |
| Rhinitis medicamentosa | Variable, with congestion | Prolonged decongestant use |
| [Foreign body](https://durgical.com/en/conditions/foreign-bodies-of-the-ear-and-nose/) | One-sided, purulent, foul | Young child |
| CSF leak | Clear, one-sided | Trauma or surgery; worse leaning forward; beta-2 transferrin |

## Red flags

- Clear one-sided discharge after head injury or nasal surgery: CSF leak with a risk of meningitis.
- Periorbital swelling, double vision, loss of vision or severe headache: complication of rhinosinusitis.
- One-sided bloody or foul discharge in an adult.
- History of recurrent meningitis.

## Next step / Initial management

- Common cold: symptomatic care; do not prescribe antibiotics.
- Uncomplicated acute bacterial rhinosinusitis: watchful waiting if follow-up is reliable; if treating, amoxicillin or amoxicillin-clavulanate.
- Allergic rhinitis: an intranasal corticosteroid first line and a second-generation antihistamine; in rhinitis medicamentosa, stop the decongestant.
- Suspected CSF leak: beta-2 transferrin, skull base CT and urgent referral to ENT or neurosurgery.
- Priority referral: one-sided bloody or obstructive discharge in an adult; urgent referral with orbital or neurological signs.

## Test yourself

Think of the answer, then tap the question to see it.

## Weeks after a skull base fracture, a 40-year-old man notices clear fluid dripping from the right nostril when he leans forward. Which test do you order?

Beta-2 transferrin in the fluid to confirm CSF; then skull base CT and urgent referral because of the risk of meningitis.

## An adult has had purulent discharge and congestion for 5 days, without high fever. Do you prescribe an antibiotic?

No. It is most likely viral; bacterial infection is suspected if it lasts more than 10 days without improving, is severe or worsens after improving.

## What is the first-line treatment of allergic rhinitis?

An intranasal corticosteroid, with a second-generation antihistamine as symptoms require.

## A 3-year-old girl has had purulent, foul discharge from the left nostril for 10 days. What do you suspect?

A nasal foreign body: one-sided foul discharge in a young child suggests it.

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## Connections

## Related 3

- [Approach to nasal blockage](https://durgical.com/en/ent/approach-to-nasal-blockage/)
- [Antibiotics in upper respiratory infections: when they help](https://durgical.com/en/ent/antibiotics-in-upper-respiratory-infections-when-they-help/)
- [Approach to loss of smell](https://durgical.com/en/ent/approach-to-loss-of-smell/)

## Related conditions 2

- [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/)
- [Common cold (acute viral rhinopharyngitis)](https://durgical.com/en/conditions/common-cold/)

[← All of ENT](https://durgical.com/en/ent/)

Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.

Sources: [Allergic Rhinitis](https://www.ncbi.nlm.nih.gov/books/NBK538186/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Rhinitis Medicamentosa](https://www.ncbi.nlm.nih.gov/books/NBK538318/) (StatPearls Publishing (NCBI Bookshelf), 2026); [Cerebrospinal Fluid Leak](https://www.ncbi.nlm.nih.gov/books/NBK538157/) (StatPearls Publishing (NCBI Bookshelf), 2025); [Outpatient Clinical Care for Adults](https://www.cdc.gov/antibiotic-use/hcp/clinical-care/adult-outpatient.html) (Centers for Disease Control and Prevention (CDC), 2024); [Outpatient Clinical Care for Pediatric Populations](https://www.cdc.gov/antibiotic-use/hcp/clinical-care/pediatric-outpatient.html) (Centers for Disease Control and Prevention (CDC), 2024); [Acute Sinusitis](https://www.ncbi.nlm.nih.gov/books/NBK547701/) (StatPearls Publishing (NCBI Bookshelf), 2025); [Nasal Foreign Body](https://www.ncbi.nlm.nih.gov/books/NBK459279/) (StatPearls Publishing (NCBI Bookshelf), 2023).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ent/approach-to-a-runny-nose-including-csf-leak/