The Enduring Appeal of Leeches

Why did bloodletting remain so popular for so long?

The Enduring Appeal of Leeches

To say that the medical practice of bloodletting has a chequered history would be an understatement. Bloodletting is, without a doubt, one of the most infamous and recognisable methods employed by our esteemed past physicians, and for people today it inspires a degree of fascination and disgust rarely matched by any other historical treatment. Yet it’s efficiency was based purely on ancient medical theory rather than practical results.


There are several cases of famous people being killed by their well-meaning physicians who were slightly too enthusiastic with their leeches. George Washington, for example, woke up with a sore throat on 13 December 1799 and was dead four days later after being drained of five to seven pints of blood. So why did bloodletting remain so popular, even into the nineteenth century when the medical theory it evolved out of had already been disproved?

The practice is first recorded in ancient Egypt and was incorporated into the writings of Greek physician Hippocrates (c.460-370 BC), who is often referred to as the ‘father of medicine’. His theory was expanded on and popularised by Galen, a physician in Rome in the second century AD, and ‘Galenic medicine’ would go on to dominate European medicine for more than a thousand years. Galen wrote that the body is comprised of four humours – black bile, yellow bile, phlegm and blood – which, when out of balance, will cause illness. Treatment often involved different types of purging, each one as unpleasant as the last, which included laxatives, emetics and, the most enduring method, bloodletting.

The practice of bloodletting can be traced back thousands of years
The practice of bloodletting can be traced back thousands of years

Contrary to popular perceptions, the majority of bloodlettings were performed with a lancet – a sharp bladed instrument – rather than leeches. However, it is leeches that have really captured the imagination of those looking back on medical history, most likely because they are seen as particularly gruesome and horrifying to modern-day sensibilities. Leeches were often used for patients considered too weak for the lancet. The intended area was rubbed with sugar water to encourage the leech to bite, after which it would be left until engorged.

As leeches became more popular and demand outstripped supply, a more cost-effective method physicians developed was to reuse the same few leeches. Once a leech was engorged with blood, salt could be rubbed across its mouth which would force it to disgorge its contents, allowing it to be reused almost immediately.

In the Middle Ages, bloodletting became the go-to treatment for most complaints, from plague to epilepsy, and there were surprisingly few amendments to Galenic theory during this time. Galenic medicine remained the dominant medical model into the seventeenth century despite crucial advancements, such as the publication of Andreas Vesalius’s illustrations of his dissections and William Harvey’s discovery of the circulation of blood, both of which fundamentally contradicted the anatomical knowledge presented by Galen. In fact, Harvey was forced to delay publishing his ground-breaking discovery for twenty years until 1628 amidst pressure from his University of Oxford colleagues that his findings were too controversial and maybe he was better off leaving well enough alone.

By the late 18th century, Galen’s theory of the four humours had been discounted by serious physicians, yet its associated treatments persisted despite the lack of any theory to support them. It is widely considered that one of the main reasons traditional methods endured for so long was because of the patients themselves. Patients are inherently conservative and suspicious of any new treatments, even if they are cheaper, less painful and proven to be more effective.

A 19th-century 'artifical leech' © Getty Images
A 19th-century ‘artifical leech’ © Getty Images

Although the enduring appeal of purging may sound inconceivable to patients today, people in this period expected different things from their medicine. Unlike 21st century patients, patients pre-20th century equated effective medicine with medicine that made them feel completely different, even if that feeling was terrible. Nowadays we associate effective medicine with a loss of symptoms. However, neither perspective is entirely accurate, for instance, modern drugs can just mask the symptoms and not do anything to address the underlying complaint.

In the spirit of fairness, it should be noted that bloodletting did work in select cases, for instance, if the patient was suffering from high blood pressure. However, for the most part, draining a sick person of their vital fluids is anathema to medical professionals today. Despite this, leeching seems to be making a comeback. In the past few years, a number of alternative therapies have espoused the virtues of bloodletting, and although their clientele may be small their arguments have a certain appeal for those disillusioned with modern medicine. Promoting the idea of natural medicine, their adherents utilise the simple yet irresistible logic that illness is caused by ‘bad blood’ that must be expelled from the body and replenished.

It’s not only alternative medicine that recognises the virtues of leeching; some surgeons use them after plastic surgery to reduce inflammation and the risk of blood clots.


It seems as if leeches are coming back in fashion.