Key takeaways

Leech therapy, also known as hirudotherapy, is utilized in modern medicine primarily to improve surgical outcomes, especially in plastic and reconstructive surgeries, by promoting blood flow and reducing venous congestion.
The saliva of leeches contains hirudin, a powerful anticoagulant that prevents blood clots, reduces inflammation, and has been studied for its potential in treating conditions like osteoarthritis and improving symptoms in people with diabetes.
Despite their ancient use for a variety of ailments, today’s medicinal leeches are bred in controlled environments and are considered medical devices by the FDA, ensuring their quality and safety for medical use.
While generally safe, leech therapy can have side effects such as risk of infection and allergic reactions, and it is covered by insurance when prescribed as part of a medical treatment, emphasizing its legitimacy and role in contemporary healthcare practices.

There’s a very good chance that in the pharmacy of a hospital near you, a temperature-controlled aquarium holds a strange (but totally legitimate!) product used to improve the outcome of certain plastic and reconstructive surgery procedures: leeches.

Yes, you read that right: leeches, those little bloodsucking worms often found in freshwater ponds. While the application of leeches in medical practice is nothing new—physicians have been sticking leeches to patients for centuries in attempts to cure an endless list of ills—the current way that leeches are used in medicine is wildly different from their historical use.

Here’s everything you didn’t realize that you wanted to know about modern leech therapy (also called “leeching”), including which conditions doctors use it for, what it does, and how well it works.

What is leech therapy?

In many ancient civilizations, including those in Egypt, China, and Greece, leeches were used in combination with bloodletting to balance the four humors, an early medical theory that was often used to explain previously-inexplicable illnesses and maladies.

Typically, the leeches would be placed on the part of the body that had the problem. Leeches would be placed on your neck, for example, if you had a sore throat. They were often used to treat fevers, too. Sometimes leeches were even used in dentistry to treat abscesses, inflammation, and tooth pain. There’s no actual evidence, though, that leeches helped improve any of these patients’ outcomes. In fact, because of a lack of knowledge about how germs spread, they often transmitted diseases and made people sicker.

Is leech therapy still used today?

When the four humors theory of medicine was debunked in favor of germ theory, the use of leeches fell from popularity. Until the 1970s, that is, when healthcare providers realized the bloodsucking power of leeches could actually help with certain surgical procedures.

Because leeches have several tiny, needle-sharp teeth, they can attach quickly to skin and tissue. Their saliva has powerful anticoagulant properties, similar to antiplatelet medications such as aspirin. It reduces inflammation and encourages proper blood flow around the leech bite. This is especially helpful when providers are attempting to reattach a severed or amputated body part, or when they are performing skin graft surgery. Today, leech therapy is sometimes referred to as hirudotherapy, after the species name of medical leeches, hirudo medicinalis.

5 leech therapy benefits

Medicinal leech therapy (MLT) today is much more sophisticated than its ancient uses. It can help to improve outcomes in the following scenarios.

1. Improves surgical outcomes

The biggest and most common use for leech therapy in modern medicine is in surgery. Plastic and reconstructive surgeons rely on leeches from time to time to improve surgical outcomes for their patients, particularly when performing microsurgery.

“When we reattach small blood vessels [in a skin graft procedure], a small percentage will get clogged in the vein,” explains Rod Rezaee, MD, the director of Head and Neck Surgical Oncology and Reconstruction at UH Cleveland Medical Center. “In order for a graft to take, blood has to get into the graft through an artery and leave the graft through a vein—if a large vein gets clogged or congested, the graft can fail.”

To prevent this venous congestion, leeches can be applied to get the blood flowing properly again and promote healthy soft tissue as the wound heals. Leeches can be applied to wide areas after reattachment or grafting, such as the leg, or after surgical procedures in more delicate areas like the fingers, scalp, or face.

“After being applied to the required site, they suck the excess blood, reducing the swelling in the tissues and promoting healing by allowing fresh, oxygenated blood to reach the area until normal circulation can be restored,” says Beatrice Adams, Pharm.D., a critical care clinical pharmacist at Tampa General Hospital.

2. Prevents blood clots

According to a 2013 study in the Indian Journal of Pharmaceutical Sciences, the protein found in leech saliva, called hirudin, has antithrombotic properties—in other words, it can prevent coagulation, or blood clots, from forming and as well as treat acute clots. As a result of this same study, many cardiovascular drugs are made with derivatives of hirudin and are used to treat patients at risk of severe types of clots, like pulmonary embolism and deep vein thrombosis.

3. Reduces pain in people with osteoarthritis

Other studies, like this one from 2011, also suggest that the proteins in leech saliva may have powerful pain relieving and anti-inflammatory benefits. Trials in patients with osteoarthritis have shown a decrease in pain, as well as a decrease in stiffness and swelling.

4. Improve symptoms in people with diabetes

Leech therapy may be a key treatment for diabetes in two ways: by reducing the amount of venous congestion in the blood and by helping to heal diabetic ulcers. Diabetics often have circulation problems because of fatty deposits in blood vessels; anything that keeps the blood flowing more easily, including leech therapy, has a potential benefit for diabetic patients.

As for wound healing, diabetics are also more likely to experience ulcers on the skin, especially on the feet. According to a 2020 study in the Journal of Traditional and Complementary Medicine, diabetics may have less success in resolving those ulcers, leaving them with chronic wounds. When used in late-stage wound healing, the study suggests that leech therapy could improve wound outcomes and prevent amputation.

5. Treat dermatologic conditions

Some practitioners of leech therapy claim that it can “cure” hair loss, hair thinning, acne, and other skin conditions like psoriasis and eczema. One small 2014 trial suggests there are potential connections between leech therapy and skin health, with eczema improving significantly after leech therapy. There’s speculation that leech saliva also works as a vasodilator, opening veins to improve circulation to the affected area.

However, the research here is pretty sparse overall, relying mostly on individual case studies. For example, one case study published in the International Journal of Pharmacognosy and Chinese Medicine reports that a woman with alopecia experienced hair regrowth after receiving leech therapy, while another credits the clearing of one woman’s acne to the use of leeches.

Where do the leeches come from?

Leeches are bred at farms specializing in medicinal leeches. Hospital pharmacies can order leeches just as they would any other medication or therapy, and they are cared for by pharmacy staff until they need to be used.

“In 2004, the FDA granted approval for the commercial marketing of medicinal leeches and deemed leeches to be medical devices,” Dr. Adams says. “Leeches are obtained from reputable medical leech producers, where they are maintained properly prior to being shipped to the hospital for their ultimate purpose; the controlled environment ensures leeches are the best quality to be used in the medical setting.”

Pharmacy staff check on the leeches several times per week, making sure the water levels are adequate and feeding them just enough, says Dr. Rezaee: “They sit in the pharmacy in a sterile, cooled environment, [which] keeps them not metabolically active, because otherwise they would use up a lot of energy and would have to eat more.”

Most pharmacies will keep just enough leeches to treat one patient since it’s impractical to keep hundreds of leeches on hand; once they are used for one patient, the leeches are then restocked.

Leech therapy side effects

Although it’s generally safe, leeches are living creatures so there are some potential side effects of leech therapy.

Change in positioning

“Nurses and physicians have to be taught how to attach the leeches and monitor them,” Dr. Rezaee says, “because there are different ways to encourage them to attach to the tissue you want them to and not to places you don’t.”

The leeches also have to be monitored closely during therapy because they may start to migrate away from the designated area and need to be repositioned.

Risk of infection

“Like any medical procedure, leech therapy comes with a risk of infection since leeches are being applied at wound sites—similar to humans, leeches carry bacteria in their bodies, [so] there is a small risk that patients could be exposed to bacteria from the leech,” Dr. Adams explains. Infection with aeromonas hydrophila is a known complication of leech therapy. To prevent this, providers use prophylactic antibiotics to prevent infection when leeches are used.

Allergic reactions

Additionally, a small number of patients may find that they are allergic to enzymes in leech saliva; this is a rare complication and usually only causes itching or mild inflammation. Prolonged bleeding after leech removal is also a rare but possible side effect, though proper medical treatment can typically resolve any persistent blood loss.

In the vast majority of cases, leech therapy is relatively uncomplicated and even painless, thanks to the analgesic effect of leech bites. “Leeches’ saliva contains pain-relieving factors, [which] is a protective mechanism for the leech so that the host…is likely to not know that it’s there,” Dr. Adams says. “The biggest challenge for patients and families tends to be the mental aspect of seeing the leech on them, which is why education is provided upfront to put patients more at ease.”

So while you may not actually forget the leeches are even there, you shouldn’t expect leech therapy to hurt. Unfortunately, the same can’t be said for the leeches: since they could transmit bloodborne pathogens from one patient to another, they can’t be reused. Dr. Rezaee explains the leeches are euthanized in an alcohol solution after use.

Does insurance cover it?

Use of medicinal leeches may be prescribed to you as part of whatever type of surgery or reconstructive treatment you’re already receiving at a hospital. All hospitals that are designated level 1 trauma centers keep leeches on hand, so that’s one way to know if yours provides this form of therapy.

And since they are, technically, prescribed to you, they are covered by insurance providers just like any other prescription. “Medicinal leeches are dispensed by the pharmacy, so it’s a medical intervention and is an accepted method of treatment as long as there is a documented need,” Dr. Rezaee says.

Other practitioners, such as naturopaths or hirudotherapists (i.e., people trained to use medicinal leeches), may offer to provide leech therapy outside of the hospital setting. These providers may or may not be medical doctors. You should only receive leech therapy under the care of a physician and through a pharmacy setting to ensure that your leeches are sterile and healthy, and that your care team knows how to safely attach and remove the leeches without risking further complications.

Leech therapy alternatives

Leech therapy isn’t always the right choice. “Leech therapy is a tool to use depending on the clinical scenario,” Dr. Rezaee says. In some situations, there are other, better options:

Surgery: For partial blockages, leeches can be a simpler way to get the blood flowing the way it’s supposed to. But, if you have a full obstruction or blockage of a vein, Dr. Rezaee says surgical revision is the standard of care, not leech therapy.
Blood thinners: In many cases coagulation inhibitors, such as heparin, are preferable to using leeches to improve blood flow.
Anti-inflammatory medication: There are lots of medications that can help conditions such as osteoarthritis, from nonsteroidal anti-inflammatories such as Advil to steroids like prednisone.

Other times, leeches are the best choice. “When we’re grafting, we want as much tissue to survive as possible to improve success, and a leech can [do that] until surgery is possible or until the body heals itself and reestablishes the blood vessel connections,” Dr. Rezaee says.