Antibiotics: when they help and when they do nothing

Bacteria versus viruses

Antibiotics kill bacteria. They have no effect whatsoever on viruses. Colds, most sore throats, most coughs, flu and COVID are viral, which is why an antibiotic will not shorten them.

Green mucus is not proof of infection

The colour comes from immune cells doing their job and appears in ordinary viral colds. It is not by itself a reason for antibiotics.

When antibiotics are genuinely needed

• Confirmed streptococcal throat infection
• Bacterial pneumonia
• Urinary tract infection with symptoms
• Skin infections such as cellulitis
• Any severe infection with high fever and rapid deterioration

Why misuse matters to you personally

Beyond resistance across the population, each course disturbs your own gut flora for weeks, can cause diarrhoea, thrush and allergic reactions, and makes a resistant infection more likely for you specifically in the following months.

Finish the course as prescribed

Follow the length your doctor set for your infection, and never reuse leftover antibiotics from a previous illness or from someone else.