Immune & gut · Healing & injury
LL-37, simplified.
Also called Cathelicidin, CAP-18
Early researchYour body’s own germ-fighting peptide, made by skin and immune cells. It is studied for infections and slow-healing wounds.
- Size
- 37 amino acids
- How it is taken
- Injection or topical
- Status
- Research compound
- Available sizes
- Vials: 5 mg
What is it?
LL-37 is the only human member of a family of natural antibiotics called cathelicidins. It pokes holes in bacteria and helps direct the immune response. CAP-18 is the name of the larger protein it is cut from.
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What studies show
- In the labKills many bacteria, fungi and some viruses in lab dishes.
- In peopleIn a small trial, applying it to chronic leg ulcers sped up healing compared with placebo.
What we don’t know yet
- Whether injecting it helps anything in people.
- Long-term safety.
Side effects and cautions
- Too much LL-37 is linked to inflammatory skin conditions like rosacea and psoriasis.
- Injection-site reactions.
Is it legal?
Not FDA-approved.
Dosage & schedule evidence
How to read published schedules
Third-party protocols are not established clinical dosing standards. Safe human dose, frequency, and duration may be unknown. Research findings may not translate to safe or effective personal use.
| Measurement | Meaning |
|---|---|
| 1 mg | 1,000 mcg (mass) |
| 100 U-100 units | 1 mL (volume, not dose) |
See third-party published protocols ↗ for research context. North Star does not validate these schedules.
Consult your doctor before considering any peptide for personal use. Educational only, not administration guidance.
Common questions
What is LL-37?
Your body’s own germ-fighting peptide, made by skin and immune cells. It is studied for infections and slow-healing wounds. LL-37 is the only human member of a family of natural antibiotics called cathelicidins. It pokes holes in bacteria and helps direct the immune response. CAP-18 is the name of the larger protein it is cut from.
What does the research say about LL-37?
Kills many bacteria, fungi and some viruses in lab dishes. In a small trial, applying it to chronic leg ulcers sped up healing compared with placebo.
Is LL-37 FDA approved?
Not FDA-approved.
What are the side effects of LL-37?
Too much LL-37 is linked to inflammatory skin conditions like rosacea and psoriasis. Injection-site reactions.
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This page explains published research in plain language. It is not medical advice, a diagnosis, or a recommendation to take anything, and it does not give dosing. Most peptides here are not FDA-approved, and products sold online vary widely in purity. Rules around peptides are changing, so check the current status and talk with a licensed clinician before starting anything. Last reviewed 2026-10-19.