Risks & Complications of Leech Therapy

All medical treatments involve some risk. The following is a list of the more common complications associated with leech therapy:


Reported incidence of infections related to leech therapy range from 2.4 to 20%. Aeromonas hydrophila is the bacteria most associated with these infections. Cases of septicemia, cellulitis and meningitis due to leech transmitted Aeromonas hydrophila have been published.

Aeromonas hydrophila is a gram negative, facultative anaerobic rod, usually sensitive to third generation cephalosporins (Ceftazidime), sulfas (Bactrim, Septra), quinolones (Cipro) and aminoglycosides. Anticipate an order for prophylactic antibiotics. Hyperbaric oxygen therapy for cellulitis has been reported to be useful when antibiotics have failed.

Aeromonas hydrophila is a normal resident in the Hirudo medicinalis gut. It is believed that contamination of the wound occurs when the leech inadvertently regurgitates gut contents into the wound. Care must be taken to avoid squeezing the leech while handling. Gently guiding the leech and allowing the leech to fully detach before removing it from the area should reduce the chance of wound infection.


Leech therapy may involve significant blood loss. A large skin flap may require 200 or more leeches over a period of about 10 days. A very large leech can extract as much as 15ml of blood and the bite may continue to ooze for days. Up to 50% of patients may require transfusions to replace red blood cells. Hemodilution with IV fluids may be used prior to and during therapy in order to dilute the blood and reduce the loss of RBCs. Daily Hgb and Hct are necessary to avoid the consequences of anemia.

Factoid - It is believed that George Washington lost 4+ quarts of blood in 24 hours as a result of leech therapy for throat infection. He died shortly thereafter. (http://www.collectmedicalantiques.com/bloodletting.html)

Leech migration:

Leeches detach themselves and there is a risk of leech movement or migration from the treatment area, possibly into body orifices or deeper into the wound itself. They may enter the ear, nose, mouth or perineum and attach to the tissue.

Leech therapy should be continuously supervised. However, patients are frequently left unattended long enough for the leech to let go and start wandering in search of a new place to rest or feast. Such an instance can increase the risk of treatment, not to mention the damage it does to the nurse/patient relationship.

If a leech attaches outside the treatment area, it's important not to pull it loose. Pulling on the leech can increase the chance of regurgitation and infection. Granzow and colleagues at the University of Miami devised a simple method to prevent the leech from wandering. They affixed one end of a surgical suture to the leech and tied the free end to a firm object or dressing, limiting the range of the leech and reducing the danger that it will migrate into unwanted areas. Other people use creative “cages” made from paper cups or gauze. With the physician's permission, sometimes putting gauze plugs into an open orifice next to where the leech is attached can prevent the leech from entering.

It is your responsibility to administer leech therapy safely. Unintended leech bite is a reportable medical error. Protect your patient and yourself by never leaving your patient unattended during leech therapy.

Instant feedback:

Leeches should never be pulled off if they attach to the wrong place.

Allergic reactions:

The most common manifestation of allergic reaction is a mild itching at the attachment site. Medicinal leeches tend to cause fewer allergic reactions than leeches of other varieties encountered in the wild. However, allergic reactions from mild to severe anaphylactic reactions can occur:

Instant feedback:

Severe allergic reactions are common with leech therapy.

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