And the prayer of faith shall save the sick.... James 5:14-15
Herbalists had existed since ancient times, and herbalism was known everywhere.
The Mesopotamians, for example, knew about hellebore, hyoscyamus, mandrake and opium.
The founder of pharmacology is generally regarded as an ancient Greek, Dioscorides, whose work was known in Latin as De Materia Medica. It detailed some six hundred plants and almost a thousand drugs.
Such knowledge was scorned by the Church, as were contemporary herbalists. Like alchemists, they were often accused of practicing witchcraft.
Had churchmen taken a more positive interest they might have learned that witches' sabbats owed their existence more to hallucinogens such as hyoscine than to Satan. They might also have learned that naturally occurring compounds can be used as antibiotics and anesthetics.
Mandrake, hemp and poppy were all alkaloids traditionally used as anesthetics. As well as hyoscine (scopolamine), modern drugs such as picrotoxin, serpasil and cocaine were all documented in ancient pharmacopeias
For many centuries the Church clung to the theory of signatures. Theologians taught that God had created certain plants with magical medicinal properties and that he had left clues to these properties. Thus a yellow blossom would cure jaundice, and a red one could improve the blood. A root shaped like a foot would relieve gout.
Like so many other beliefs of the Church, this one was utterly mistaken and served only to hold up progress. Objective research was pointless because the Church already knew the answers. Pharmacy therefore remained static, confined in a straitjacket of error.
The Church retarded and even regressed other areas of medicine, rejecting sophisticated rational ideas of ancient times. Ancient peoples had practiced surgery, including cataract operations, brain surgery and plastic surgery. They used ligatures. They were aware of the importance of public health and personal hygiene.
Followers of Hippocrates held that every illness has a natural cause. Christianity rejected all of this. In their view illness was indisputably caused by sin, diabolical possession, witchcraft and other satanic forces. To deny it was to invite the attentions of the Inquisition.
http://www.badnewsaboutchristianity.com/ea0_trad.htm