From leeches to barber-surgeons: The deadly world of medieval medicine

At the heart of medieval medical belief lay the theory of the Four Humors, which was actually based on the writings of Hippocrates and Galen who taught that the body contained four fluids: blood, phlegm, yellow bile, and black bile.

Each humor corresponded to an element; it also aligned with a season and showed in personality traits.

Good health, they argued, required a balance of these humors, with black bile thought to originate in the spleen and influence melancholic temperaments.

Avicenna’s Canon of Medicine was translated into Latin during the twelfth century and became a standard university text that combined Galenic theory with Arabic medical knowledge. 

Diagnosis began with identifying which humor had become too much or too little.

Physicians examined urine samples through a practice called uroscopy, comparing colour, smell, and even taste to guides in medical charts.

They used bloodletting to reduce an excess of blood, purging to remove harmful substances through vomiting or diarrhoea, and diets designed to counteract the supposed imbalance.

A patient considered too cold and moist might receive spicy, dry foods to restore balance.

Treatments followed strict idea-based rules rather than observations of actual disease patterns, which limited how well they worked. 

Within medieval society, the Catholic Church played a major role in medical practice.

Monasteries maintained sick wards where monks treated the sick by using prayer and herbal remedies and by studying classical medical texts.

Hospitals attached to religious houses cared for travellers, the poor, and the sick; they provided hands-on treatment and spiritual care.

Institutions such as the Hôtel-Dieu in Paris, founded in 651, became models for later hospitals in Europe. 

Clerics studied medical works in Latin, which kept knowledge from ancient times and the Islamic world.

Belief that illness arose from sin or divine punishment supported healing prayers, pilgrimages, and relics as treatments.

Interestingly, the Fourth Lateran Council of 1215 banned priests from performing surgery that involved blood, which encouraged the growth of secular surgeons.

Universities such as Bologna and Montpellier taught medicine with some freedom, which allowed the study of classical texts to continue. 

Formal education for physicians took place at universities such as Salerno, Bologna, and Montpellier mentioned just before.

In particular, the School of Salerno had already gained fame by the eleventh century as a centre of medical learning.

Students spent several years reading Latin translations of Greek and Arabic texts, which built their theoretical knowledge, while anatomical dissection became more common after the early fourteenth century, when scholars such as Mondino de’ Luzzi carried out public dissections in Bologna in 1315. 

Practical training also took place through on-the-job apprenticeships. Young men worked with physicians, apothecaries, or barber-surgeons to gain experience.

Unfortunately, women rarely attended universities but learned medical skills through informal means, especially in midwifery and the preparation of herbal remedies.

This kind of knowledge often passed orally within families or communities, and midwives in some towns swore oaths of good conduct before local authorities. 

Medical practitioners varied greatly in background and duties. Wealthy patients consulted university-educated physicians who diagnosed illnesses, predicted outcomes, and prescribed treatments.

Apothecaries prepared and sold medicines made from herbs, minerals, and animal products.

They sometimes created mixed remedies such as theriac, a blend of many ingredients believed to cure poisoning and disease. 

Meanwhile, barber-surgeons carried out procedures such as bloodletting, tooth extraction, and amputations.

However, they also treated wounds and performed minor surgeries, tasks that learned physicians considered beneath their status.

They used lancets, bone saws, and cautery irons for their procedures, while leeches became more common in later centuries because they were easy to apply and remove.

Midwives gained experience by practicing and then assisted women during childbirth.

Finally, local folk healers treated poorer communities using herbs, charms, and traditional remedies, which often relying on knowledge of plants such as willow bark for pain relief or honey for wounds. 

Medieval Europe suffered common outbreaks of diseases that had no successful treatment.

Plague, leprosy, dysentery, and smallpox caused widespread death. The Black Death killed around 30 to 60 percent of Europe’s population between 1347 and 1351, and spread faster than any physician could understand.

Explanations for such epidemics included foul air, planetary movements, or divine punishment.

Towns often established leper houses outside their walls to isolate sufferers. 

In the absence of any other cure, physicians sometimes prescribed carrying sweet-smelling herbs such as rosemary or lavender to protect against plague.

Quarantine measures occasionally slowed disease, but they rarely prevented large outbreaks. 

The Middle Ages preserved knowledge that would have been lost after the fall of Rome.

Scholars translated Greek and Arabic medical texts into Latin, which kept this knowledge available for later physicians.

Universities created traditions of formal medical education that continued into the Renaissance, while monastic hospitals provided models for organised healthcare in towns and cities. 

Even the practical experience gained by barber-surgeons contributed to the development of later surgical techniques.

Specifically, Mondino de’ Luzzi’s dissections influenced later anatomists such as Vesalius, who corrected errors in Galen’s work.

Although medieval treatments often harmed patients, the period created systems for learning, practicing, and controlling medicine that shaped later developments in Europe.