LL-37
WellnessAlso known as: Cathelicidin, Human Cathelicidin, CAP18 Fragment
Emerging ResearchWhat is LL-37?
A naturally occurring antimicrobial peptide produced by the human immune system. Part of the cathelicidin family, LL-37 plays a role in innate immune defense against bacteria, viruses, and fungi. Being explored for immune support and wound healing.
How it works
Disrupts microbial membranes through direct electrostatic interaction with bacterial cell walls. Also modulates immune responses by recruiting immune cells to infection sites, promoting wound healing via angiogenesis, and neutralizing bacterial endotoxins (LPS).
What marketers claim
- ▸natural antibiotic alternative
- ▸kills all bacteria and viruses
- ▸cures Lyme disease
- ▸eliminates biofilms completely
What evidence supports
- ✓broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria in vitro
- ✓disrupts bacterial biofilms in laboratory settings
- ✓promotes wound healing via angiogenesis and keratinocyte migration in cell studies
- ✓endogenous LL-37 deficiency is associated with increased infection susceptibility
Research evidence
Key studies on LL-37, summarized in plain language. This is not an exhaustive list — it highlights the most relevant findings.
LL-37 antimicrobial activity and biofilm disruption in vitro
Finding: LL-37 demonstrated bactericidal activity against Staphylococcus aureus, Pseudomonas aeruginosa, and E. coli at micromolar concentrations. Also disrupted established biofilms of P. aeruginosa by 60-80%.
Limitation: In vitro concentrations required for biofilm disruption may not be achievable or safe in vivo. Serum proteins can bind and inactivate LL-37.
Cathelicidin LL-37 in wound healing and angiogenesis
Finding: Topical LL-37 application accelerated wound closure and increased vascularization in mouse cutaneous wound models compared to controls.
Limitation: Mouse skin physiology differs significantly from human skin. Topical delivery and systemic injection may have very different efficacy profiles.
Best for
Safety notes & concerns
Full safety guide →- ⚠no FDA-approved therapeutic applications
- ⚠human clinical trials for exogenous administration are extremely limited
- ⚠injectable LL-37 from compounding pharmacies has variable quality and purity
- ⚠at high concentrations, LL-37 can be cytotoxic to human cells
- ⚠overexpression is associated with autoimmune conditions including psoriasis and rosacea
- ⚠claims about treating chronic infections like Lyme disease are not supported by clinical evidence
Pairs well with
Use caution with
Frequently asked questions
Can LL-37 treat Lyme disease?
There is no clinical evidence that exogenous LL-37 treats Lyme disease. While LL-37 shows antimicrobial activity in laboratory settings, in vitro activity against Borrelia does not translate to treating an established infection in humans. Lyme disease requires proper antibiotic treatment prescribed by a physician.
Is LL-37 the same as vitamin D's immune effect?
Vitamin D does upregulate LL-37 production in the body — this is one mechanism by which vitamin D supports immune function. However, taking exogenous LL-37 via injection is very different from the body producing it naturally via vitamin D signaling. The two are related but not equivalent approaches.
How is LL-37 administered?
In research and biohacking contexts, LL-37 is typically administered via subcutaneous injection. Oral administration would likely result in degradation by digestive enzymes. There is no established dosing protocol for humans as clinical trials are lacking.
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Last updated: 2025-03-25
Medical Disclaimer
The information on this site is for educational and informational purposes only. It is not intended as medical advice and should not be used to diagnose, treat, or prevent any condition. Always consult with a qualified healthcare professional before starting any new supplement, peptide, or treatment protocol.