LL-37
LL-37 (Human Cathelicidin Antimicrobial Peptide)
Also called LL-37, cathelicidin, hCAP18, CAP-18
The body's own antimicrobial peptide
LL-37 is one of the body's own antibiotics. Immune cells make it and release it where bacteria are, and in laboratory work it kills them by punching holes in their membranes rather than by interfering with their chemistry, which makes resistance harder to develop. It has been studied for infections, biofilms and wound healing, and it is not an approved medicine.
The body's own broad-spectrum antimicrobial peptide: the active fragment of human cathelicidin (the CAMP gene), part of innate immune defence against bacteria, viruses and biofilms. The body makes it in a vitamin-D-dependent way, through the vitamin D receptor. Injected LL-37 is experimental, with thin human safety data, and it is not an approved medicine.
- Status
- Not FDA-approved
Early research, mostly in the lab so far
What LL-37 has been studied for
The reasons people look it up, roughly in order of how often, and what research exists for each. Interest in a use is not evidence that it works; the evidence is stated under each one.
- Biofilms and stubborn infections
- The main reason people look it up. Biofilms are bacterial colonies wrapped in a protective layer that ordinary antibiotics struggle to penetrate; in laboratory work LL-37 disrupts membranes and biofilms. Human trial evidence for infections is limited.
- Wound healing
- It also signals for repair and new blood vessel growth, which is why it turns up in wound-care research, including small human studies of topical use on leg ulcers.
- Gut
- Discussed for the gut on the reasoning that it targets unwanted bacteria without the collateral damage of a broad antibiotic. Reasoning rather than trial evidence.
Mechanism of Action
How LL-37 works
LL-37 is a front-line innate immune molecule:
- Direct antimicrobial action. In laboratory work it disrupts bacterial and viral membranes and breaks down biofilms across a broad range of pathogens.
- Immune signalling. It recruits immune cells and tunes the inflammatory response, bridging innate and adaptive immunity.
- Vitamin D dependence. The CAMP gene that produces cathelicidin is switched on by active vitamin D through the vitamin D receptor, so the body's own LL-37 production tracks the vitamin D system.
LL-37 side effects: what studies reported
The most consistently reported problem is the injection site, worse than with most peptides, because the same membrane-disrupting action that kills bacteria also irritates human tissue.
Most commonly reported
- Injection-site pain, redness and swelling, more pronounced than with most peptides
- Flu-like aching in the first day
- Fatigue
- Headache
Worth keeping an eye on
- It is pro-inflammatory as well as antimicrobial. In people with an inflammatory or autoimmune condition it can push the wrong way
- Raised LL-37 is implicated in psoriasis and rosacea
Dose-related findings. Membrane irritation is concentration-dependent in laboratory studies.
Source: Reports outside trials and the pharmacology; no large human trial of injected LL-37. This is a summary of published findings, not a complete safety profile and not medical advice. Questions about LL-37 belong with a licensed clinician who knows your history.
Your Genetics & LL-37
The genes involved in how LL-37 works
LL-37 works through the receptors these genes build, and the genes vary from person to person. Researchers have linked some of that variation to differences in how people respond. A DNA report tells you which versions you carry.
VDR · ••
The vitamin D receptor switches on the CAMP gene that makes LL-37. VDR variants such as this one have been studied for their association with vitamin D related traits, with mixed results. No study has tested whether they change response to LL-37.
GC · ••
The GC gene builds vitamin D binding protein, and this variant is associated with differences in circulating vitamin D levels in population studies. Any effect on LL-37 production is inferred from the pathway, not measured.
CAMP is the gene that encodes LL-37 itself. Variants are studied for their association with cathelicidin levels; the evidence is early.
The dots after each gene are where your own result goes. Your report fills them in with the two letters you carry at that position.
Which of these variants do you carry?
Your report reads the DNA file you already have against this research.
Often discussed alongside
Compounds that come up next to LL-37 in research and discussion. Each has its own page. None of this is a suggestion to combine them.
KPV
also studied for inflammationEmerging EvidenceKPV (Lys-Pro-Val)
A three-amino-acid fragment snipped off the end of a hormone your body already makes. Almost every page describes it as switching on a melanocortin receptor; the research fairly clearly says it does not. What it appears to do instead is more interesting, and it is why nearly all the data are about the gut rather than skin. No human study of KPV has been published.
4
Gene variants
15+
Studies
Access
Access and legal status
LL-37 is not an FDA-approved drug. Products sold online as “research chemicals” are labelled not for human use, and FDA treats them as unapproved drugs when they are marketed for people. We don't link to any seller, and nothing on this page is a recommendation to obtain or use it.
Your DNA and LL-37: see which of the variants studied alongside it you carry, and what that research does and does not show. Read my DNA, $99 →
Educational information only, not medical advice. Most peptides are not FDA-approved. Do not start, stop or change any medication or peptide because of this page; talk to a licensed clinician.
Worth knowing about LL-37
Interactions and situations where there is a specific reason to be careful. Where the honest answer is that nobody has studied something, it says so and says what that leaves open.
- It cuts both ways on inflammation
- Raised LL-37 is implicated in psoriasis and rosacea, which is a specific reason for caution in people with inflammatory skin conditions.
- Not an approved medicine
- It is not approved by any major regulator, and human data on injected LL-37 are thin. A persistent infection needs a medical diagnosis.
Last updated
Frequently Asked Questions
What has LL-37 been studied for?
LL-37 is the body's natural broad-spectrum antimicrobial peptide. It has been studied in the laboratory against bacteria and biofilms, and in small human studies of topical use on chronic leg ulcers. It is produced by the body's own cells in a vitamin-D-dependent way, and injected LL-37 is experimental.
How is LL-37 linked to vitamin D?
The CAMP gene that makes LL-37 is switched on by active vitamin D through the vitamin D receptor, so the body's own LL-37 production depends on the vitamin D system. VDR and GC variants have been studied for their association with vitamin D related traits; no study has tested whether they change response to injected LL-37.
Is LL-37 legal?
LL-37 is not approved as a medicine by any major regulator. Human data are thin and injected use is experimental.
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Your DNA and LL-37
What the research says about your variants.
The report
Which LL-37 variants do you carry?
Your report reads the DNA file you already have against the published research on 31 peptides, marker by marker, and says what that research does and does not show.
Read my DNA, $99