14 Facts About Antibiotics

This article is general information, not medical advice. Always take antibiotics exactly as your doctor or pharmacist tells you.

Antibiotics are medicines that kill bacteria or stop them from multiplying. Before they existed, a scratch, a sore throat or childbirth could lead to a fatal infection. Today they are one of the foundations of modern medicine, but bacteria are fighting back. Here are 14 facts about antibiotics.

1Penicillin was discovered by accident.

In September 1928 Alexander Fleming returned to his laboratory at St Mary’s Hospital in London after a holiday and noticed that a mould had grown on one of his dishes of bacteria. Around the mould, the bacteria had been killed. The mould was Penicillium, and the substance it made became known as penicillin.

2It took another decade to turn it into a medicine.

Fleming struggled to purify penicillin. At the University of Oxford, Howard Florey, Ernst Chain and their team, including Norman Heatley, worked out how to produce and purify it around 1940 and showed that it could cure infections. Fleming, Florey and Chain shared the 1945 Nobel Prize in Physiology or Medicine.

3The first patient was a police officer from Oxford.

In 1941 Albert Alexander, a police constable with a severe infection, became the first person treated with purified penicillin. He began to recover, but supplies were so scarce that they ran out and he later died. Mass production in the United States during the Second World War solved the shortage.

4Fleming predicted resistance in 1945.

In his Nobel lecture, Fleming warned that using too little penicillin, or using it when it was not needed, could make bacteria resistant to it. His warning came true within a few years.

5Antibiotics do not work on viruses.

Colds, flu, most coughs and most sore throats are caused by viruses, so antibiotics will not help with them. Taking antibiotics when you do not need them can cause side effects and helps resistant bacteria to spread.

6It is the bacteria, not you, that become resistant.

A common myth is that your body gets “used to” antibiotics. In fact, it is the bacteria that change. When antibiotics are used, the bacteria that survive can multiply and pass their resistance on, even to other kinds of bacteria.

7Resistant infections kill more than a million people a year.

A major study published in The Lancet in 2024 found that antimicrobial resistance directly caused 1.14 million deaths worldwide in 2021. Without action, it estimated that resistant infections could cause 39 million deaths between 2025 and 2050.

8Many antibiotics come from the soil.

Bacteria and fungi in the soil make chemicals to fight off their rivals, and many of our antibiotics come from them. Streptomycin, the first effective treatment for tuberculosis, was found in soil bacteria in 1943. Scientists are still searching soil for new antibiotics today.

9A doctor drank bacteria to prove a point.

In the early 1980s most doctors believed that stomach ulcers were caused by stress. The Australian doctor Barry Marshall drank a culture of the bacterium Helicobacter pylori, developed stomach inflammation, and helped prove that the bacterium causes ulcers that can be treated with antibiotics. He and Robin Warren won the Nobel Prize in 2005.

10Some Civil War soldiers had glowing wounds.

After the Battle of Shiloh in 1862, some wounded soldiers reported that their wounds glowed in the dark, and those soldiers seemed more likely to survive. In 2001 two American school students suggested a cause: a glowing bacterium called Photorhabdus luminescens, which produces chemicals that kill other bacteria.

11Farm animals receive a large share of antibiotics.

Worldwide, a large proportion of antibiotics is given to farm animals, sometimes to help them grow faster. Using antibiotics to promote growth has been banned in the UK and EU since 2006, and UK sales of antibiotics for farm animals have fallen by more than half since 2014.

12You should never save or share leftover antibiotics.

The NHS advises taking antibiotics exactly as prescribed, never keeping them for later and never sharing them with anyone else. Any you have left over should be taken back to a pharmacy to be disposed of safely.

13Most people with a penicillin allergy label are not allergic.

About 1 in 10 people in the UK have a penicillin allergy recorded in their medical notes, but when they are tested, more than 9 in 10 of them turn out not to be allergic. Being wrongly labelled means they may be given less effective antibiotics.

14Honey is used in some wound dressings.

Medical-grade honey, which is sterilised, is used in some dressings because it has antibacterial properties. Honey from the kitchen cupboard is not sterile and should not be put on wounds.

FAQs about antibiotics

What are the common side effects of antibiotics?

The most common side effects include diarrhoea, feeling sick, bloating and indigestion. Some people have an allergic reaction. Speak to a pharmacist or GP if you are worried about side effects.

Can I drink alcohol while taking antibiotics?

It depends on the antibiotic. With most, drinking a little is unlikely to cause problems, but some, such as metronidazole, can react badly with alcohol. Check the leaflet or ask your pharmacist.

How do antibiotics kill bacteria?

Different antibiotics work in different ways. Some, like penicillin, stop bacteria from building their cell walls. Others block the machinery bacteria use to make proteins or copy their DNA.

Sources and further reading

Explore more: facts about malaria and facts about COVID-19.

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