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Have you ever heard of leeches? Leeches are small worm-like animals that can attach themselves to the human body and suck out blood.

Leeches can attach themselves to a human body and suck out blood for 30 minutes to an hour, removing about 20 ml of blood before they fall off. They attach themselves to the skin using two muscular suckers. They then bite the skin through three teeth that are inside one of these suckers. Leeches can actually ingest about five times their body weight in blood before they let go of the skin and fall off.

These little creatures have had a long and strange history in the medical field. The first recorded use of medicinal leeches was about 2500 years ago, although there is some evidence that the ancient Egyptians and Aztecs may have used these little blood-sucking creatures to help people that were having medical problems. Back then, leeches were used to remove the “bad blood” from patients that were suffering from things as basic as a headache.

The practice of “bloodletting”, which is removing blood from the human body, was very common in the mid 1800’s. In fact, the practice of “bloodletting” was so common that in 1833 alone, France imported over 42 million leeches. Other methods of “bloodletting” were also widely used during this time, but none were as efficient, predictable, and painless as the leeches. Leech harvesting also became a very popular and lucrative activity during this time. People would walk around in leech infested waters (leeches live in warm, shallow, sheltered water areas) and then remove the leeches that had attached themselves to their legs and feet. The popularity of “bloodletting” using leeches, however, was soon to end.

The practice of “bloodletting” lost its popular in the early 1900’s. It was seen as an old and outdated procedure that had no benefit to the patient. By the early 1920’s, the practice of “bloodletting” was almost never used. It was not until the mid 1980’s that we would see the return of these small blood-sucking creatures.

In 1986, Dr. Charles Lent of Utah State University reported in the journal Nature that leeches can be useful after the transplantation and reattachment of tissues. Lent reported that leeches can help to restore normal blood flow in certain damaged parts of the body. Basically, leeches can help because they have a natural anticoagulant (a substance that prevents blood from clotting and forming scabs) in their saliva. When leeches attach to the skin, they can help repair the venous (veins are part of your circulatory system and are where the blood flows through on the way back to your heart) system in the damaged area. Once normal venous flow is restored in the damaged area of the body, the leech can be removed. Some surgeons now occasionally use these little creatures to help with certain procedures. So, the next time you see a picture of a leech, don’t scream and yell “Yuck”. These little creatures can actually help us.