Keloid and Hypertrophic Scarring
Investigational use for stable keloid and hypertrophic scars; case-series evidence for softening and flattening.
Patient Summary
- Is this FDA-cleared for this use?
- Not FDA-cleared for keloid or hypertrophic scars. FDA cleared medicinal leeches only for venous congestion in microsurgical reconstruction (K040187, 2004). Use for scar modification is investigational.
- What evidence exists?
- Tier C (investigational). Three small uncontrolled case series describe scar-height reductions and Vancouver Scar Scale score improvements; there are no randomized controlled trials. Evidence-based first-line therapy for keloid and hypertrophic scars is intralesional triamcinolone (sometimes combined with 5-fluorouracil), silicone gel sheeting or silicone gel, pressure therapy, and for keloids resistant to medical therapy, surgical excision combined with adjuvant radiation or intralesional steroid. Cryotherapy and laser therapies are additional options for hypertrophic scars.
- Main risks
- Bleeding from bite sites for 6 to 24 hours after detachment
- Bruising and tenderness over the scar area for 5 to 10 days
- Worsening of the keloid (paradoxical growth — keloids have unpredictable response to trauma)
- New keloid formation at the bite sites themselves in keloid-prone individuals
- Local skin infection or, rarely, Aeromonas infection
- Allergic reaction to leech saliva (uncommon)
- Post-inflammatory hyperpigmentation, especially in darker Fitzpatrick skin types
- Delay or replacement of evidence-based intralesional therapy
- Who should not consider this
- Patients within 6 weeks of scar revision surgery
- Patients with active scar infection or drainage
- Patients with strong keloid diathesis (multiple keloids, family history of severe keloids) — bite scars may keloidize
- Patients with darker Fitzpatrick skin types at high risk of post-inflammatory hyperpigmentation
- Patients on anticoagulants, with hemophilia, or with severe anemia
- Patients who have not tried evidence-based intralesional steroid or silicone therapy
- What to ask your clinician
- Has my scar been classified as keloid (extends beyond original wound) or hypertrophic (within wound boundary)?
- How old is the scar? Mature keloids (over 2 years) respond less to any therapy.
- Have I tried intralesional triamcinolone (with or without 5-FU)? It is first-line and well-evidenced.
- Have I tried silicone gel sheeting or pressure garments for at least 3 months?
- If keloid is severe, am I a candidate for excision with adjuvant radiation or intralesional steroid?
- What is my keloid recurrence risk after any intervention?
- What is the practitioner's experience and Aeromonas-prevention plan?
- When to seek urgent care
- Rapidly growing scar with pain, color change, or ulceration (rule out malignancy)
- Spreading redness, warmth, pus, or red streaks (cellulitis)
- Bleeding from a bite site lasting more than 24 to 48 hours
- Fever above 38.0 C / 100.4 F or chills
- Sudden severe pain or itching unresponsive to usual measures
- Hives, throat tightness, or breathing difficulty
What this does NOT mean
- This is not FDA-cleared for keloid or hypertrophic scars.
- Small uncontrolled series with modest score improvements do NOT establish efficacy versus intralesional triamcinolone or silicone therapy.
- Mechanism rationale (ECM remodeling, antifibrotic peptides) does NOT establish clinical equivalence to proven therapies.
- Keloid-prone patients may develop new keloids at bite sites — this risk is real and unpredictable.
- Leech therapy is not a substitute for intralesional steroid, silicone, pressure therapy, surgical excision with adjuvant therapy, or laser when indicated.
Safety cross-references
Clinical Profile
- Category
- dermatological
- ICD-10
- L91.0, L98.0
- Safety tier
- low
Evidence Summary
No controlled clinical trial or credible case series of leech therapy for keloid or hypertrophic scarring has been published; there is no reliable evidence of scar-height reduction or improvement in Vancouver Scar Scale scores. Any proposed mechanism (salivary enzyme or peptide effects on extracellular matrix remodeling, or reduction of local microvascular congestion) is speculative and unproven in this condition. Established first-line and adjunctive measures (intralesional triamcinolone, silicone gel sheeting, pressure therapy, and, in selected cases, surgical excision with adjuvant treatment) remain the standard and should be directed by a dermatologist. ASH position: any use of leech therapy for keloid or hypertrophic scars is investigational and mechanistic only.
Treatment specifics
How many leeches, where they are placed, how long a session lasts, and whether to repeat are clinical decisions made by a qualified provider under institutional protocol — not something to self-administer. Discuss the specifics with a clinician experienced in medicinal leech therapy. (Clinicians: switch the audience selector in the top bar to “Clinician” to view protocol detail.)
Key Trials
- Hosseini SV et al. (2017), n=24
Contraindications
- Active anticoagulant therapy (warfarin INR >2.0, DOACs, heparin)
- Hemophilia or other bleeding disorder
- Severe anemia (Hb <10 g/dL)
- Active bacteremia or sepsis
- Known hypersensitivity to leech salivary proteins
- Pregnancy (relative — first/third trimester)
- Immunocompromised state with severe neutropenia
- Active scar infection
- Within 6 weeks of scar revision surgery
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