Antiseptic means against or opposed to (anti) infection or being infected (septic). Antiseptics prevent infections by killing the microbes-mainly bacteria-responsible for them. In this post I describe:
- History of Antiseptics
- Modern Antiseptics
- How do Do Antiseptics Work?
- And Other Uses of Antiseptics
In general, the word “antiseptic” is used for a substance that kills harmful microbes or stops them growing and that can be applied directly to an infected part of the body, without too much damage to body tissues; “germicide” means much the same as antiseptics.
A substance with similar germ-killing properties to an antiseptic that is given as a drug, to be carried around the body in the bloodstream to infected parts, is called an Antibiotic. Another group of substances used for killing harmful microbes is disinfectants. These are generally not used on living tissues since they are too strong. Instead, they are used on floors, toilets, sinks and so on.
There are many different types of antiseptic. Most are chemicals, such as phenol, alcohol, chlorine, and formaldehyde, and are used as water solutions. Superheated steam (steam under pressure), ultraviolet light and other types of radiation also act as antiseptics.
HISTORY of ANTISEPTICS
For centuries before the discovery of the “germ theory” people used antiseptics without knowing why they worked. “Pickling”, which is soaking meat in a strong solution of salt and spices, destroyed enough bacteria to stop the meat going bad, thereby preserving it. The development of modern antiseptics began with the brilliant work of Louis Pasteur, who was the first to show that microscopic living things are capable of causing disease. He also showed that heating, for example of raw milk, kills many disease-causing microbes. From this comes the process of “pasteurization” that makes our milk safe. (There is a separate article on PASTEUR, LOUIS.)
Several years before Pasteur announced his discovery, a Hungarian doctor named Ignaz Philipp Semmelweis made a very important observation. At that time, (about 1847) at least one woman in ten who had a baby in hospital died from the serious disease which called puerperal fever. Semmelweis made each doctor wash his hands in chlorine water before touching a patient. After this only one woman in 100 died from the fever.
Shortly after Pasteur’s work, in the 1860s, the British surgeon Joseph Lister carried out several experiments that changed surgery enormously. Having heard of Pasteur’s work, Lister became convinced that bacteria were responsible for the infections that killed many patients undergoing operations. He began to use antiseptics in an attempt to destroy bacteria in infected wounds. Later he soaked surgical instruments in antiseptic solution and washed his hands in it before operating. He also sprayed the air in the operating theatre, the operating table, and the patient’s skin with antiseptic. As a result, the number of infections after surgery dropped greatly. The antiseptic Lister used was carbolic acid (phenol). This is hardly ever used today because it is not a very efficient germ-killer, and it is almost as harmful to human tissues as it is to microbes.
Many chemicals have antiseptic qualities. But not all are safe because they injure normal human tissue. Modern antiseptics must be good at killing microbes but bad at killing human cells.
No one antiseptic is “best”. Antiseptics are chosen depending on the particular job at hand. Soap is probably one of the best-known and most commonly used antiseptics. Alcohol is another. Before a doctor gives someone an injection, he or she will probably rub the skin with a little cotton wool soaked in alcohol. Hexachlorophene, chemicals containing chlorine, and iodine are also used as skin antiseptics. In addition, hydrogen peroxide, potassium permanganate, and chemicals containing mercury and silver act as antiseptics and are sometimes used in medicine. However, many antiseptics have been replaced by more effective and less harmful (to the patient) antibiotics.
The color of an antiseptic has nothing to do with its power. Mercurochrome, which is red, is quite weak, while Zephiran, which is colorless, is one of the most powerful.
How Do Antiseptics Work?
It is not known exactly how chemical antiseptics work. They may interfere with the microbe’s own cellular chemistry so that it cannot carry out its life processes. Or they may act directly on the microbe, dissolving its outer cell membrane or “skin”.
Unfortunately, many antiseptics have the same effects on human cells, which is why they must be used with care. Very weak antiseptics can be used inside the body, but most cannot. When swallowed or injected, some antiseptics can cause serious illness and even death.
Other Uses of Antiseptics
Antiseptics have many uses other than strictly medical ones. Sewage may be treated with powerful antiseptics to make it free of disease-carrying microbes. Drinking water is treated with chlorine (at very low concentrations) to kill harmful microbes in it, and so is the water is swimming pools.
In order to preserve food, any bacteria in it must be destroyed or prevented from growing. The freezing of food quickly prevents bacteria from growing but does not kill them. Recently various types of radiation have been used to kill bacteria in and on food so that it keeps for longer.
Antiseptics play a very important part in our daily lives, and new ones are constantly being developed.