Rhazes

Abu Bakr Muhammad ibn Zakariyya al-Razi, better known as Rhazes, was a leading figure in the field of medicine during the tenth century. He wrote the first-known description of small pox and was the first to describe and define allergies, particularly hay fever. He was also credited with being the first to use animal gut for sutures and plaster to construct casts.
More Famous Firsts