At the age of 25 he became a Bachelor of Medicine and entered the Royal College of Surgeons.
In 1854, Lister became first assistant surgeon to James Syme (1799-1870), a leader of surgery in England. The two became close friends and Lister ended up marrying Syme's daughter Agnes, leaving the Quakers because his religion did not permit alliances with nonmembers.
After six years he got a professorship of surgery at Glasgow. At the time the usual explanation for wound infection was that the exposed tissues were damaged by chemicals in the air or via a stinking "miasma" in the air. The sick wards actually smelled bad, not due to a "miasma" but due to the rotting of wounds. Hospital wards were occasionally aired out at midday but Florence Nightingale's doctrine of fresh air was still science fiction then. Facilities for washing hands or the patient's wounds did not exist and it was even considered unnecessary for the surgeon to wash his hands before he saw a patient. This was strange because the work of Ignaz Philipp Semmelweis and Oliver Wendell Holmes were not heeded even though the parellel should have been obvious.
Lister became aware of a paper published by Louis Pasteur which showed that rotting and fermentation could occur without any oxygen if micro-organisms were present. Lister confirmed this with his own experiments. If micro-organisms were causing gangrene, the problem was how to get rid of them. Pasteur suggested three methods: to filter them out, to heat them up or expose them to chemical solutions. The first two were inappropriate in a human wound so Lister experimented with the third.
Carbolic acid (phenol) had been in use as a means of deodorising sewage, so Lister tested the results of spraying instruments, the surgical incisions, and dressings with a solution of it. Lister found that carbolic acid solution swabbed on wounds markedly reduced the incidence of gangrene and subsequently published a series of articles on the Antiseptic Principle of the Practice of Surgery describing this procedure on March 16 1867 in the journal The Lancet.
He also made surgeons wear clean gloves and wash their hands before and after operations with 5% carbolic acid solutions. Instruments were also washed in the same solution and assistants sprayed the solution in the operating theatre.
Many of his contemporaries laughed at him but Lister was said to have never bothered to reply and only heaved an occasional sigh at the world's stupidity. His critics still believed in the theory of spontaneous generation.
Lister left Glasgow in 1869 to succeed Syme in Edinburgh. His fame had spread by then and audiences of 400 often came to hear him lecture. He moved to King's College in London and became the second man in England to operate on a brain tumour. He also developed a method of repairing kneecaps with metal wire and improved the technique of mastectomy. His discoveries were greatly praised and he was made Baron Lister of Lyme Regis and became one of the twelve original members of the Order of Merit.
Lister retired from practice after his wife, who had long helped him in research, died in 1893 during one of the few vacations they allowed themselves. Studying and writing lost appeal for him and he sank into religious melancholy. Despite suffering a stroke, he still came into the public light from time to time. Edward VII came down with appendicitis two days before his coronation. The surgeons did not dare operate without consulting England's leading surgical authority. The king later told Lister "I know that if it had not been for you and your work, I wouldn't be sitting here today".
A British Institution of Preventive Medicine, previously named after Edward Jenner was renamed in 1899 in honour of Lister.
Two postage stamps were issued in September 1965 to honour Lister for his contributions to antiseptic surgery.
As the germ theory of disease became more widely accepted, it was realised that infection could be better avoided by preventing bacteria from getting into wounds in the first place. This led to the rise of sterile surgery. Some consider Lister the father of modern antisepsis.
Listerine mouthwash is named after him for his work in antisepsis.