After completing his M.D. Hahnemann started his medical practice in a small town. During that era, medical practitioners adopted harsh and cruel methods to treat the sick, which were not only ineffective but also had harmful effects on patients. Hahnemann was extremely disappointed by the then prevailing system of medicine and decided to leave his practice. He started studying chemistry and wrote many articles/essays regarding the same subject.
In 1790, while he was translating a book, Cullen's Materia Medica, he came across an observation made by the author that cinchona bark cures 'swamp fever' (malaria) because it is bitter and has tonic effect on the stomach. In his quest for the true explanation, Dr. Hahnemann ingested 4 drachms of juice of the bark and was surprised to find that he himself developed symptoms of 'malaria fever'. This experiment gave rise to the idea; that a substance cured an illness in a sick person because it was capable of producing symptoms, similar to the illness in an apparently healthy individual. This experiment led him to establish the principle of 'SIMILIA SIMILIBUS CURANTUR' (like cures like) in 1796 and thus a new system of medicine 'HomoeopaTHY' originated.
Later, he made important contributions in terms of translations, articles, books, and discovered curative values of many medicines. During this period Hahnemann had to face a lot of opposition from allopathic physicians but he stood firm and faced it with lot of grit and courage. However, he received a strong support not only from his disciples, but also from his first wife who was a great moral support to him during this struggling period.
Hahnemann's long and sustained efforts bore fruit in the form of the first 'Homoeopathic Hospital' in 1832 and many Homoeopathic colleges opened all over Europe thereafter
Hahnemann could not settle down his practice at one place because of his medical rivals, but this did not deter him from successfully spreading Homoeopathy. He was very popular amongst patients, and people from all over the world came to seek treatment from him. He got married for the second time at the age of 80 years and his second wife supported him in his journey thereafter.