Quinine side effects include deafness, low blood platelets, and an irregular heartbeat. Use can make one more prone to sunburn. While it is unclear if use during pregnancy causes harm to the baby, use to treat malaria during pregnancy is still recommended. Quinine is an alkaloid, a naturally occurring chemical compound. How it works as a medicine is not entirely clear. Quinine was first isolated in 1820 from the bark of a cinchona tree. Bark extracts have been used to treat malaria since at least 1632. It is on the World Health Organization's List of Essential Medicines, the most effective and
Jesuit's bark long conflict over the good or harm effected by Peruvian Bark". The Spanish Jesuit missionaries in Peru were taught the healing power of the bark by natives, between 1620 and 1630, when a Jesuit at Loxa was indebted to its use for his cure from an attack of malaria ("Loxa Bark"). It was used at the recommendation of the Jesuits in 1630, when the Countess of Chinchon (Cinchon; the derivative is Cinchona, the appellation selected by Carl Linnaeus in 1742; Clements Markham preferred Chinchona), wife of the new viceroy, who had just arrived from Europe, was taken ill with malaria