Leech Therapy Simply Explained

1. What It Is About

Leeches are small animals that attach to the skin and suck blood. In medicine they are used mainly for musculoskeletal complaints, that is, in joints, tendons and muscles. The leech bites and holds on, sucks blood and releases saliva into the small wound. This saliva contains many different substances. They inhibit blood clotting, thus preventing the blood from clumping, and they promote local blood flow. Treatment usually lasts 30 to 90 minutes. Afterwards the leech falls off by itself or is removed. The site may itch, redden or continue to bleed. The exact mechanism of action is not fully understood. Experts assume that several factors act together: blood loss, improved local blood flow and the substances in the saliva. Saliva composition varies between animals, which makes comparisons between studies difficult.

2. What Studies Show

The best-studied sites are the knee joint, the carpometacarpal joint of the thumb and the insertion of the forearm extensor tendon at the elbow (tennis elbow). For joint degeneration, termed osteoarthritis in medical language, several randomised studies exist. In one study with 51 people with knee osteoarthritis a single leech treatment was compared with a 28-day pain-relieving ointment. After seven days pain had decreased markedly more in the leech group than in the comparison group, and the advantage persisted until day 91. The study was not blinded, meaning all participants knew who received which treatment 1. Another study examined women with osteoarthritis of the carpometacarpal joint of the thumb. Here too, symptoms were relieved more in the leech group than with the pain-relieving ointment, and the difference was still evident on day 60 2. In a study with 113 people with advanced knee osteoarthritis participants received leeches once, twice at four-week intervals, or a sham treatment with an artificial leech. All three groups improved, yet the improvements in the leech groups were greater and still detectable after 26 weeks. Analgesic requirements also fell 3. A review pooled several controlled trials totalling 237 people with knee osteoarthritis. It found clear pain reduction and better physical function shortly after treatment; longer-term differences were smaller 4. For tennis elbow, 40 people received a single leech treatment or a 30-day course of pain-relieving ointment. Pain decreased more in the leech group and the advantage remained measurable until day 45 5. In reconstructive surgery leeches are used when a transplanted skin flap has insufficient venous drainage. In an observational study of 8 patients all flaps survived 7. A review cites success rates of 65 to 85 percent, yet notes that blood transfusions were required in half the cases 8.

3. What Remains Unclear

In almost all studies participants knew whether they received leeches. This can make results appear more favourable. Only one study included a sham treatment 3. Direct comparisons with physiotherapy or intra-articular injections are still lacking. Outcomes beyond six months have likewise not been examined. For complaints outside the musculoskeletal system, for example involving the heart or skin, only isolated observations exist from which no firm conclusions can be drawn. Tolerability is also not fully clarified: a pooled analysis of several studies with 264 people found more adverse effects in the leech group, chiefly itching, continued bleeding, infections and allergic reactions 6. Because saliva composition and animal origin vary, standardised delivery of treatment is difficult.

4. What This Means in Practice

Two points help to interpret the findings. Pain relief in knee, thumb and elbow complaints has been observed in several studies measured shortly after treatment and up to several weeks later. This is the area where results most consistently agree. Everything beyond this time frame has so far been described only in isolated observations. In reconstructive surgery leeches are used when venous drainage of a transplanted skin flap cannot otherwise be secured; this application requires close supervision 7. The next step would be to clarify how leech therapy compares directly with physiotherapy or intra-articular injection and whether blinded studies confirm the observed benefits.

All Details with Study Numbers and Sources: detailed page on leech therapy. For Children: Leech Therapy for Children.