In 1348, doctors had no understanding of bacteria or how the plague actually spread. Their treatments were built on a medical framework that had been dominant for over a thousand years: the theory that illness came from an imbalance of four bodily fluids, or “humors.” Every remedy they tried, from bleeding patients to burning aromatic herbs, followed logically from that flawed premise. None of it worked against the bacterium responsible for killing roughly a third of Europe’s population.
The Medical Theory Behind Every Treatment
Medieval physicians believed the human body contained four essential fluids: blood, phlegm, yellow bile, and black bile. Each corresponded to an element (air, water, fire, earth) and had specific qualities like hot, cold, moist, or dry. Health meant these fluids were in balance. Disease meant something had thrown them off.
The prevailing explanation for the plague was “miasma,” or poisoned air. Both Hippocrates and Galen had taught that bad air caused pestilence, and Arab medical scholars accepted the same idea, making it the most authoritative model available. Physicians theorized that the corrupt air resulted from a disturbance in the balance of the four elements, which then disrupted the humors inside each person who breathed it in. They pointed to specific sources of this bad air: southern winds, fumes rising from swamps, rotting plants and animal carcasses, cesspools, sewers, and dung heaps. The physician Gentile of Foligno, who himself died of plague in 1348, believed that corrupt air could even be released locally by opening long-sealed caverns, wells, or rooms in houses.
This framework shaped every treatment decision. If bad air caused the imbalance, you purified the air. If the humors were corrupted, you drained them out.
Bloodletting and Lancing Buboes
Phlebotomy, the deliberate opening of a vein to drain blood, was one of the most common medical procedures of the era. Physicians believed that removing blood could restore humoral balance by expelling corrupted fluid from the body. In practice, it weakened patients who were already gravely ill. Later physicians would note that drawing blood from infected patients risked “loss of strength, if not of life,” but in 1348 it remained standard practice.
The plague’s most distinctive symptom was the bubo: a painful, swollen lymph node, often in the groin, armpit, or neck, that could grow to the size of an egg. Doctors attempted to draw out what they believed was poisonous matter trapped inside. The first approach was typically a blister plaster, a topical preparation designed to irritate the skin and draw pus to the surface. When plasters and their accompanying ointments failed, physicians resorted to surgery. They would cut the bubo open with a blade or burn it open with a heated instrument (a cautery), drain the pus, and then dress the wound. The thinking was straightforward: the more pus that came out, the better the patient’s chances. In reality, some patients may have survived this approach simply because their immune systems were already fighting off the infection, not because the lancing helped.
Purifying the Air
Since miasma was considered the root cause, an enormous amount of effort went into making the air “safe” to breathe. People burned juniper, oak, and other aromatic woods in their homes and in the streets, hoping the smoke would overpower or neutralize the poisonous atmosphere. Physicians advised patients to carry pomanders, small personal containers filled with mixtures of precious herbs and spices. A typical pomander held separate compartments for rosemary, rose petals, lemon peel, and other fragrant materials. Wealthier individuals had ornate metal pomanders; poorer people might simply carry bundles of dried herbs.
Doctors also recommended sprinkling vinegar and rosewater around living spaces. Some advised holding sponges soaked in vinegar to the nose when venturing outside. The logic was consistent: if poison entered through the air, pleasant or sharp smells could serve as a barrier. It’s worth noting that the iconic beaked plague doctor mask, often associated with the Black Death in popular culture, did not exist in 1348. The first mention of that costume dates to a 1619 outbreak in Paris, and the first written description of an herb-stuffed beak mask comes from a Roman epidemic in the 1650s.
Theriac and Herbal Remedies
The most prestigious medicine available in 1348 was theriac, a compound drug with ancient origins. The recipe traced back to the court of King Mithridates VI, whose personal physician created an antidote with roughly 40 ingredients. By the time of the Roman physician Galen, the formula had ballooned to over 70 ingredients, including viper flesh, opium, honey, wine, and cinnamon. The finished product was supposed to mature for years before use, and it was taken either as an oral potion or applied topically as a plaster.
Theriac was expensive and difficult to obtain, so it was mainly available to the wealthy. For everyone else, local healers prepared simpler herbal mixtures. Vinegar-based washes were common. Crushed herbs, ground minerals, and various plant extracts were mixed into poultices and applied to buboes or taken internally. None of these had any real effect on the Yersinia pestis bacterium causing the plague, but theriac’s opium content may have at least dulled the considerable pain patients experienced.
Dietary Rules and Lifestyle Restrictions
Medieval physicians issued detailed instructions about daily habits, believing that diet and behavior could protect humoral balance against the corrupting air. The Paris medical faculty, consulted by the French king, produced a widely circulated report with specific guidance. People were told to avoid going outside in the cool of the evening, at night, and in the early morning, when the air was thought to be most dangerous.
The dietary restrictions were extensive and specific. Patients were warned against eating poultry, waterfowl, young pork, old beef, and fatty meat in general. Olive oil was declared “fatal.” Daytime sleeping was considered harmful. Fasting and extreme dietary restriction were also discouraged, along with anxiety, anger, and heavy drinking. The overall picture was one of careful moderation: keep the body calm, avoid anything that might generate internal heat or moisture, and stay away from foods thought to produce excess humors.
Quarantine: The One Measure That Helped
Among all the responses to the Black Death, the most effective was also the simplest. In March 1348, the city-state of Venice ordered that ships arriving from plague-afflicted cities had to remain moored in the Venetian lagoon for 30 days before anyone could come ashore. This was extended to 40 days over time, possibly for practical reasons or possibly out of superstition around the number 40. The Italian word “quarantina,” meaning a period of roughly 40 days, is the origin of our modern word “quarantine.”
Venice and other Mediterranean port cities couldn’t explain why isolation worked within their medical framework, but the practical results were observable. Cities that restricted movement and contact fared better than those that didn’t. It was the one intervention from 1348 that carried forward into modern public health, even though the people who invented it had no idea they were blocking a bacterium transmitted by fleas.
Religious Responses as Medicine
For many people in 1348, the plague was fundamentally God’s punishment for human sin, which meant the cure had to be spiritual. Prayer, fasting, pilgrimages, and public processions were all treated as legitimate remedies alongside anything a physician might offer. The most dramatic expression of this belief was the flagellant movement. Groups of flagellants traveled from town to town, publicly whipping themselves to share in Christ’s suffering and appease what they believed was divine wrath. They processed through streets, performed elaborate rituals around their dead, and attracted large followings.
The flagellant movement grew so large and unruly that the Pope eventually condemned it, but in 1348 it represented a genuinely popular response to the crisis. For people who couldn’t afford a physician and had no access to theriac or pomanders, self-punishment and prayer were the most accessible “treatments” available. The church also offered practical comfort: prayers for the dead were believed to shorten a soul’s time in purgatory, which provided emotional relief to survivors even if it did nothing against the disease itself.