A leech is all stomach.



EDWARD JENNER (1749-1823)

The leech disturbed is newly risen
Quite to the summit of his prison.

Roman women dyed their hair black using a paste made from leeches.


For 2,000 years the most common medical practice performed by doctors was actively harmful to patients. The justification was that the balance of the humours (blood, phlegm, black bile and yellow bile) was the key to health, and blood was the dominant humour and so the one that most needed controlling. The worse the disease, the more blood had to be let. The practice began to be discredited in the second half of the 19th century, but there are serious medical texts which continue to recommend it as late as 1923.
It was thought that removal of so much blood as to cause the patient to faint was beneficial (the fainting being seen as relaxing). This involved removing really large quantities of blood – several pints – so most blood-letting was done by cutting, opening up a vein or artery in a specific place for each ailment. Leeches, by contrast, are a somewhat ineffectual means of extracting blood; each one will only remove about a teaspoonful. So leeches were used more for localized adjustments than for serious bleeding – but where they were used, they were used 50 at a time.
Although generally discredited, leeches made a comeback in the 1980s for a different purpose. In microsurgery such as plastic and reconstructive surgeries, where one of the problems is inefficient drainage of the veins. This can lead to a blockage which causes the tissue to die. To prevent this leeches are applied to drain off excess blood. They can also be used to treat black eyes.

Bogey vs Leeches

John Houston's classic The African Queen won Humphrey Bogart his only Oscar. While filming the famous ‘filthy leeches’ scene, the leeches wouldn't bite Bogie and so, despite flying a leech-breeder in from London, they had to stick rubber leeches all over him. It's possible the leeches didn't respond to his skin because of the amount of alcohol he consumed during the shoot. Everyone on the film fell sick except for him and Houston. They attributed this to all the whisky they drank that they’d brought with them. Bogart said 'Whenever a fly bit Huston or me, it dropped dead’.

To catch a leech

Catching a leech is a tricky business. In the 19th century doctors suggested they liked beer, or recommended smearing one’s arm with sour cream to attract them. In 1994 two Norwegian researchers conducted a trial to test the traditional methods. They used beer, Guinness, sour cream and garlic. When soaked in beer, leeches behaved 'erratically'; they started swaying and took twice as long to bite. Some fell off the target’s arm altogether. In short, they were drunk. The sour cream made no difference but the garlic proved fatal. Although the two test leeches initially seemed attracted to the garlic-smeared forearm, they were unable to feed properly, and both died within 2.5 hours of contact. This may be where the traditional use of garlic as a guard against blood-sucking vampires originated.
In 1998 three researchers filled sheep-skin condoms with blood and put them in water with leeches. By heating the blood and waggling the condom around, they showed that neither temperature nor movement attracted leeches but that, when they rubbed the condom on a frog first, leeches came to feed immediately.
Leech gathering was a big industry in Wales and north west England, albeit lo-tech. People would stand in lakes and pools and wait for leeches to attach to their legs, after which they plucked them off, put them in baskets and sold them to doctors. 

SAMUEL BUTLER (1835-1902)

A skillful leech is better far, than half a hundred men of war.

Wild leeches have the same protected status as the white rhino. A few remain in Scotland and Romney Marsh in Kent.

A single leech is run by a mere 15,000 neurons (honey bees' brains contain 950,000).


I don't think most people associate me with leeches or how to get them off. But I know how to get them off. I'm an expert at it.

Leech on a Leash

To prevent leeches crawling into patients' orifices, 19th-century doctors developed the leech-on-a-leash, pushing a bit of thread through the leech's tail. Some surgeons treated this method as a way to apply leeches within the body. In 1833 one Dublin surgeon, Jonathan Osborne, treated inflamed intestines by putting a leashed leech up the patient’s bottom. He said 'I have never used more than four leeches at once', which must have been comforting.

These days, when leeches are used to encourage capillary growth after patients have had a finger (or other member) reattached, surgeons still tie a little lasso around them, so the leash method survives. Or they simply stitch them to the patient’s body.

British hospitals buy up to 15,000 leeches annually from Britain's only leech farm, the Biopharm leech farm near Swansea. They cost £9.95 each.

Leech Mania

France in the early 19th century went leech-crazy. Vast numbers were imported; in 1827, France imported 33,600,000 leeches - in 1829, 44,600,000, and in 1832, 57,500,000.  Leech mania saw fashionable Parisian women wearing dresses with leeches embroidered on them, or ribbons which were made to look like chains of leeches. 
This was in large part thanks to a doctor called Francois-Joseph-Victor Broussais (1772-1838), who believed that all diseases were caused by inflammation. The root problem was the stomach, as when it got inflamed the problem quickly spread to other organs. Happily, he had come up with the cure; all that was necessary was to apply leeches to remove the inflammation.
His patients were probably happy, largely because (as with other ‘cures’ like homoeopathy) leeches didn't do a huge amount of harm, unless you applied dozens and dozens of them, and many other contemporary treatments were much more dangerous. This meant that leeches may have had a better succes rate than other treatments despite not being any actual use.
Broussais put leeches on his fighting cocks every week to keep them fit. (It didn't work; they got very pale and wan). He also supposedly prescribed himself 50 to 60 leeches when he had indigestion. 


Whatever killed those people is still in that lake. And it’s going to take more than dynamite to get it out.

In the 19th century it was proposed that leeches be applied to certain areas of criminals' brain to suck away criminal tendencies.

Leech saliva contains anaesthetic, and has anti-coagulant properties that prevents blood from clotting.

Applied orally, leeches were used to treat bronchitis or coughs. Up the bottom, they were applied to inflamed bowels or difficult prostates.


Never had anything you doctors didn't try to cure with leeches. A leech on my ear for earache, a leech on my bottom for constipation.

Leeches are protandrous hermaphrodites, meaning they start with male sex organs, then in later life female ones appear.

Leeches were applied to men's scrotums for strained testicles. One doctor wrote, 'a more convenient part of the body does not present itself for this purpose.'

Medicinal leeches, Hirudo medicinalis, have five pairs of eyes, nine pairs of testicles, and a sucker at either end.

Handle with care

When you detect leeches and they are already dining on you it is ok to peel or pull them off (you use a fingernail to break the seal on the oral sucker and then flick the leech away) but you’ll keep on bleeding from the bite, sometimes for hours because of the anti-coagulant the leeches use. On the other hand, if you let the leech finish its meal and detach by itself it will ‘close’ the wound and you won’t lose an unnecessary drop of blood. One technique used in films and books is to burn the leech off with a cigarette, but this (or salt, vinegar, etc) can cause the leech to regurgitate its stomach contents into the wound and increase the risk of infection, so it isn’t recommended.
Bdellatomy is the practice of cutting a leech so that it bleeds at one end and continues to suck at the other. A sucking leech eventually gets full of blood, bdellatomy prevents this. Bdella is Greek for a leech.

Leechy Myths

1) It isn’t true that if you pull them off your skin, they’ll leave part of themselves embedded in your flesh (unlike ticks, which can leave their heads behind).

2) Leeches do not transmit disease from one host to another.

3) They don’t drop out of trees onto their hosts/prey. They can’t climb trees, and aren’t pursuing a deliberate strategy when they attach themselves to you – it’s pretty much an accident.

4) They can't jump onto you.


Of the 600 leech species identified, only about 15 are bloodsuckers. Lots of others just eat small insects whole.

The world's largest leech is the Giant Amazon leech (Haementeria ghilianii), which gets up to 18 inches long.