Imagine this Leach attached to your knee.

Medicine can be aggravatingly slow to change and it can take years for new diagnostic or therapeutic interventions to percolate through the medical community. It can take equally long for old practices to fade. I have tried to follow the dictum of “be neither the first to try nor the last to abandon a therapy.”

But nothing in the real world rivals that of the pseudo-medical world, who follow the dictum “be the first to try and the last to abandon a therapy.”

New, often preliminary, findings are spun into grand diagnostic and treatment plans, especially in the world of naturopathy, where there is a fondness for innumerable one cause of all disease.

And the old is never abandoned, although there is a weird propensity for various pseudo-medicines to combine to produce a new mutant strain of pseudo-medicine. But leeches?

Who knew that leeches were still a thing?

No, seriously, leeches

Leeches have legitimate medical uses, primarily to aid in reattachment of digits and other surgeries where there is vascular congestion. Surgeons can attach the arterial flow much better than the venous but this leads to accumulation of blood due to lack of good venous return. A leech sucks up the accumulating blood and their spit contains an anticoagulant, hirudin, as well as other biologically active products. Much easier to apply than thousands of mosquitos.

I know of leeches from the risk of infection with Aeromonas. I remember opening the refrigerator on the trauma unit years ago and found a bag o’ leeches. Gave me the willies, flashing back to the African Queen, second only to Gone With the Wind as the most disturbing and traumatic movie from my childhood.

But old school uses, from the time of Theodoric of York, as well as new therapeutic mutations, of leech therapy persist.

I came across “Comparison of the effectiveness of medicinal leech and TENS therapy in the treatment of primary osteoarthritis of the knee : A randomized controlled trial” and did a double take.

I have seen leeches used in my hospital after finger reattachment to help decrease blood engorgement in the finger. But osteoarthritis? I would have thought it would have been so Middle Ages. But no pseudo-medicine ever dies.

TENS is transcutaneous electrical nerve stimulation, a form of analgesia that is likely not all that analgesic. There are many forms of TENS, including high-frequency transcutaneous electrical nerve stimulation (h-TENS), low-frequency transcutaneous electrical nerve stimulation (l-TENS), neuromuscular electrical stimulation (NMES), interferential current (IFC), pulsed electrical stimulation (PES), and noninvasive interactive neurostimulation (NIN). Kind of reminds me of the multitudinous forms acupunctures.

One meta-analysis suggests:

Although the recommendation level of the other ES therapies is either uncertain (h-TENS) or not appropriate (l-TENS, NMES, PES and NIN) for pain relief…

and my goto for analysis of pain modalities, Paul Ingraham’s, looked at all the meta-analyses and found that TENS:

…doesn’t look great: five disappointingly non-positive,16 two spankings for back pain and osteoarthritis, and just the one clearly positive review out of seven (which is also one of the oldest and perhaps the least picky).

And concludes:

My official position for now is that it probably works well enough for some patients to be worth trying if you’re desperate…but keep your expectations low. There are solid reasons to doubt that TENS can work well.

Not a ringing endorsement for TENS but a good comparator for another pseudo-medicine. I suspect that there is a general inaccurate belief in the medical world that TENS, like acupuncture, is effective for pain. Relieving, not causing, pain. So if the pseudo-medicine is equal to TENS, then it must be effective.

A tale of two placebos

The problem, of course, is comparing two interventions with no placebo will always show benefit, especially when comparing two placebos.

And the same problem here:

Leech therapy relieves symptoms in patients with osteoarthritis of the knee and is as effective as TENS therapy in the management of osteoarthritis of the knee.

But would you even expect leech therapy, aka hirudotherapy, to work? Leech saliva does have analgesic effects. After all, Charlie didn’t know he had leeches until after he got out of the water. I would be skeptical that a topical application of leech spit would have efficacy in deep joint pain. As one study noted:

There is still no definitive explanation for the pain-reducing effect of leech therapy

There is actually a randomized study that used an artificial leech(!). Patients had one leech treatment, two treatments separated by four weeks or an artificial leech. All three had improvement and not unexpectedly, those with two interventions had a better response. The more theatrical the placebo, the better the response.

As is always the case with pseudo-medical studies, they cannot wrap their heads around the idea that when an intervention is no better than placebo, it doesn’t work:

Leech therapy can reduce symptoms caused by osteoarthritis. Repeated use of the leeches appears to improve the long-term results. We have not determined whether the positive outcome of the leech therapy is caused by active substances released during the leeching, the placebo effect, or the high expectations placed on this unusual treatment form.

The answer is staring them in the face but they can’t see it.

If acupuncture is a theatrical placebo, leeches are would be the Royal Shakespeare Theater of placebo. So no surprise leeches were beneficial in chronic tennis elbow pain in another study with no blinding or placebo.

Although given the complex constituents of leech spit, I am not totally skeptical of their use in pain. And the curious report of a positive bone scan after leech therapy suggests a deeper tissue response to leech spit is not out of the question, although I have seen a variety of positive bone scans obtained during superficial inflammation. It is safe to say that leeches for pain is not a robust literature. But there is a growing literature, as I am sure some proponent will note.

Leeches for pain? OK. Maybe. Given the nature of leech spit it might have been worth a look-see. But outside of musculoskeletal pain?

No really…leeches?

From 2015. This century. Just two years ago. A review on Pubmed suggests leech therapy, based on balancing body humours, yes body humours of blood, bile, black bile and phlegm, is indicated for:

scabies, psoriasis, eczematous dermatitis, chronic ulcers, ring worms, reddish freckles and favus… asthma, acute rhino pharyngitis and spasmodic coryza… and hypertension, migraines, phlebitis, varicose veins, arthritis, haemorrhoids, and ovarian cysts

Because leeches are good for local evacuation of morbid humours to improve illness. But given the growing literature on meridians and qi, I shouldn’t be all that flabbergasted.

Is there any support in the medical literature for leeches? Besides the occasional researcher with the last name of Leech? For the most part no. And there are a lot of researchers named Leech.

There was a useless

open labeled clinical trial study without control group was conducted with 27 patients

that suggested leeches decreased symptoms of eczema, but with such a design no real conclusions can be drawn. The plural of anecdote and all that.

They note one contraindication of leech therapy is:

Patient refusal to undergo leech therapy.

How nice of them.

And leeches are more like us, or at least me, than I had supposed

Keeping leeches in a saucer of fresh beer for some time, makes them active.

IPA or PBR now that their brewery is closed?

Leech therapy is not without complications besides local infections. There is one case of pyoderma gangrenosum, a disease every bit as awful as its name would suggest. Prior exposure to leech spit can lead to allergic reactions and care must be taken to prevent migrating leeches. Ewe. Migrating leeches. The case of the disappearing leech is not a Sherlock Holmes adventure I want to read. Migration is problem that can be cured with a leech condo although I would suggest building a wall and make the leeches pay for it. And to avoid these complications, some have even developed an electronic leech, probably to treat cyborgs. This world is too weird.

And reading the complications of natural acquisition of wild leeches makes the African Queen seem tame. Ocular leech infestations? And recurrent (!) penile self-amputation? There are some things I just do not want to know.

Not surprisingly, the use of leeches for a broad range of disease has become the purview of naturopaths. There are hints on the pubmeds where leeches are used for vertigo, tinnitus, and arthosis.

Plug ‘leech’ and ‘naturopathy ‘into the Googles and you will find Leech Naturopathy, based on Total Flow medicine. At Healthy Life naturopathy leeches are recommended for a wide variety of diseases, including “Infringement of blood pressure”. Leech therapy is available at a number of other naturopathic clinics, although much to my surprise, none in Oregon, ND or otherwise. Given the propensity of NDs to offer unique services to set them apart from the competition, it surprises me that none have latched on to this ancient and natural therapy.

Perhaps it represents a metaphor that hits to close to home.





  • Mark Crislip, MD has been a practicing Infectious Disease specialist in Portland, Oregon, from 1990 to 2023. He has been voted a US News and World Report best US doctor, best ID doctor in Portland Magazine multiple times, has multiple teaching awards and, most importantly,  the ‘Attending Most Likely To Tell It Like It Is’ by the medical residents at his hospital. His multi-media empire can be found at

Posted by Mark Crislip

Mark Crislip, MD has been a practicing Infectious Disease specialist in Portland, Oregon, from 1990 to 2023. He has been voted a US News and World Report best US doctor, best ID doctor in Portland Magazine multiple times, has multiple teaching awards and, most importantly,  the ‘Attending Most Likely To Tell It Like It Is’ by the medical residents at his hospital. His multi-media empire can be found at