Al-Razi's famous discovery was the difference between smallpox and measles, but he also contributed many other discoveries and theories. During the Islamic Golden Age, al-Razi was a physician, a teacher of medicine and an alchemist. Al-Razi studied sulfuric acid and discovered ethanol. Another discovery attributed to al-Razi was the discovery of kerosene as well as several other chemicals and compounds.
In differentiating smallpox and measles, al-Razi was the first to use humoralism, which was a crude and inaccurate process that doctors used to distinguish one contagious disease from another. He also helped further the study of ophthalmology and paediatrics.
During his medicinal teachings, he wrote or co-authored several medical books, articles and other print materials for those going into medicine or those who were in the profession and needed guidance. These writings are all from the 14th century, which was when al-Razi was a famous physician.
In addition to his discovery of the differences between smallpox and measles, al-Razi also discovered allergic asthma and how a fever helps to fight off infection. He wrote various publications on the causes of seasonal rhinitis, or hay fever. He wrote a book about what happens to some people after smelling a rose, which he called "Sense of Smelling."