Preventing and treating diseases

Many types of medicines and chemicals have been developed to help prevent and treat diseases.


Chemicals that kill microorganisms outside the body are known as antiseptics. Antiseptics can be used to clean an open wound as well as surfaces on objects such as toilets.

One simple way to reduce the risk of infection is to maintain personal hygiene and to keep hospitals clean. In the 19th century, Ignaz Semmelweis realised the importance of cleanliness in hospitals. However, although his ideas were successful, they were ignored at the time because people did not know that diseases were caused by pathogens that could be killed.

Antiseptics therefore help to prevent the spread of disease.


Antibiotics are medicines that interfere with the growth of bacterial cells. This means that the bacteria die as they cannot reproduce. Antibiotics can therefore be used to treat bacterial infections such as Salmonella food poisoning and tuberculosis. Antibiotics will only kill bacterial cells. This means that these medicines will not work against fungi or viruses.

How some common antibiotics work

AntibioticHow it works
PenicillinBreaks down cell walls
ErythromycinStops protein synthesis
NeomycinStops protein synthesis
VancomycinStops protein synthesis
CiprofloxacinStops DNA replication


From under a microscope, penicillin eroding a bacterial cell.
A bacterium damaged and distorted by penicillin

The first antibiotic - penicillin - was discovered in 1928 by Alexander Fleming. He noticed that some bacteria he had left in a petri dish had been killed by naturally occurring Penicillium mould.

Since the discovery of penicillin, many other antibiotics have been discovered or developed. Most antibiotics used in medicine have been altered chemically to make them more effective and safer for humans.


It is difficult to develop drugs that can kill viruses. This is because the virus infects a cell and hijacks the cell's machinery in order to create more copies of itself. Destroying the virus will often mean destroying the cell that the virus is inside of. Antivirals are drugs that stop viruses from replicating. They can be used to treat viral infections. Antivirals are specific to one type of virus.