The first of these discoveries was made by a Viennese physician, Semmelwei, in 1847. It seems obvious: washing hands with soap. But, at the time, there was great controversy, and many of his peers refused to believe him. When comparing the number of women who died in childbirth at two different maternity hospitals, Semmelwei noticed that, at those where the physicians performed post-mortem examinations in the morning and deliveries in the afternoon, the mortality rate was much higher. 


The solution was to order the mandatory washing of hands with soap and water before each delivery. Today, we know that this simple act - as well as other habits of personal and social hygiene, such as water and sanitation - has led to an enormous reduction in disease transmission.

The second great contribution came from Louis Pasteur, also during the nineteenth century. The discoveries made by this French scientist enabled major advances in Chemistry and Medicine. It was he who created the first vaccines, such as the rabies vaccine, which permitted the eradication or reduction of many fatal transmissible diseases. 


Thanks to vaccines, we were able to eradicate smallpox worldwide in 1980, thus saving around two million lives per year. 

Former CUF medical post in Barreiro

In many other countries, vaccines also led to the disappearance of diseases such as poliomyelitis, yellow fever, measles and tetanus. But Louis Pasteur did not stop there. It was also he who invented pasteurisation, which destroys pathogenic microorganisms in various foods, such as milk, preventing their decomposition.

The discovery of penicillin in the twentieth century, by Alexander Fleming, was another of the great revolutions in Medicine. Research relating to antibiotics began en masse and, by the 1950s, they were already being widely used for therapeutic purposes.

Very often, a simple superficial wound that became infected could lead to death; on other occasions, the cause of death was related to more serious infections, such as tuberculosis or syphilis, for example. Antibiotics had a drastic impact, given that bacterial infections were the main cause of death at the time and these medicines were - and are - an efficient weapon against them. 

Making water drinkable by adding chlorine represented the greatest advance in Public Health in the twentieth century. It was only made possible thanks to Chemistry. Chlorine - and its by-products, such as sodium hypochlorite - eliminate pathogenic agents in water and make it safe for human consumption.


In developed countries, all water that flows from the taps is treated with chlorine and, as a result, we have managed to defeat cholera, typhoid and legionella, among other maladies. Due to its advantage of being cheap and easy to apply, Chlorine has spread around the globe. And, in addition to purifying the water we drink, it is also used in the treatment of water used for recreation and sports, such as swimming pools, and water for industrial use and refrigeration

The use of soap to wash our hands, and all other habits of hygiene and water and sanitation, vaccines, antibiotics and the purification of water with chlorine represent four milestones in the history of the Sciences. Thanks to these four achievements, Humanity is safer and healthier. Thanks to these four discoveries, humans have a better quality of life and a longer life span.