Antibiotics are still handed out for blocked noses, sore throats and coloured mucus, even though the common cold is caused by viruses.
A large review of trials confirms what guidelines have been saying for years: antibiotics do not help people get better from a cold or acute purulent rhinitis, and they increase side effects.
Researchers searched medical databases for randomised controlled trials comparing antibiotics with placebo in people who:
- Had symptoms of an upper respiratory infection for less than seven days, or
- Had acute purulent rhinitis (thick, coloured nasal discharge) for less than ten days
In total they analysed:
- Six trials of the common cold involving 1,147 participants
- Five trials of acute purulent rhinitis involving 791 participants
They looked at symptom improvement, cure rates and any side effects.
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Do antibiotics improve cold symptoms
No. Across the studies of the common cold:
- Antibiotics did not shorten the illness
- They did not significantly improve general symptoms or specific nose and throat symptoms in adults or children
In adults, antibiotics increased the risk of side effects such as diarrhoea, rash or thrush compared with placebo. In children, side effects were less clear, but there was still no benefit.
The trials of acute purulent rhinitis told a similar story.
Routine antibiotic use in the first week or so did not meaningfully change outcomes but did increase the risk of harm.
What about “green snot”
Many people – and some clinicians – see coloured nasal discharge and assume a bacterial infection.
The review found that:
- Coloured mucus on its own is not a good reason to prescribe antibiotics in the first ten days
- Most of these infections are still viral and settle on their own
There is some evidence that antibiotics may help a small subgroup of people with purulent rhinitis if symptoms drag on beyond ten days without any sign of improvement, as this is more likely to reflect bacterial sinusitis.
That is a different situation from a typical cold.
Why this matters
Overusing antibiotics has two big consequences:
- It exposes individuals to side effects without benefit
- It drives antibiotic resistance, making these medicines less effective when they are genuinely needed
For people with diabetes, unnecessary antibiotics also add risk: they can trigger diarrhoea, disturb glucose control and, in some cases, increase the risk of infections like thrush.
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The authors note that many of the trials had weaknesses, including:
- Small sample sizes
- Problems with randomisation and blinding
- Inclusion of some patients who probably had bacterial throat or sinus infections rather than simple colds
These issues could actually make antibiotics look better than they are. Even so, the overall picture is clear: for garden-variety colds and short-lived purulent rhinitis, antibiotics do not help.
Study: Kenealy T, Arroll B. Cochrane Database of Systematic Reviews 2025.
