Also called Cathelicidin LL-37, hCAP18 (parent protein), Ropocamptide
A germ-fighting peptide your body makes; in people, only tested as a wound gel.
LL-37 is a natural germ-fighting peptide, 37 amino acids long, and the only one of its type humans make. Its name comes from its first two building blocks (two leucines) and its length. White blood cells and skin cells release it as a first line of defense against bacteria, viruses and fungi.
It punches holes in the outer walls of many germs. It also acts as a messenger that calls in immune cells and helps wounds close and grow new blood vessels. That cuts both ways: in some people, too much LL-37 feeds skin and autoimmune inflammation, like psoriasis and rosacea.
Some human studies
In people, LL-37 has only been tested on the skin of hard-to-heal leg ulcers: a small 2014 trial in 34 patients looked good at the lowest dose, but a bigger 2021 trial in 148 patients found no overall healing benefit over placebo, with a possible benefit only in large wounds. It was safe on the skin in both, but injected LL-37, which is how most people use it, has no published human trials. Lab research also links too much LL-37 to psoriasis and lupus-type inflammation.
Why: This is the dose most often reported in clinic and community use. It's kept low on purpose, because higher amounts can drive inflammation, and it has never been tested in a human trial.
Start at the low end, and change one thing at a time. If you take medication or have a health condition, check with a doctor first.
Set up for a 5 mg vial. Change any number to match yours. New to this? Read how to mix a vial and mg vs mL vs units first.
Pick your dose and how long you'll run it. We'll count what you need.
Get help right away for swelling of the face or throat, trouble breathing, chest pain, or a spreading, hot, red injection site.
Powder: freezer, out of the light. Once mixed with bacteriostatic water: fridge, and use within about 2–4 weeks.
FDA: Not approved. FDA removed it from its Category 2 compounding risk list in April 2026 after the nomination was withdrawn. It is not on the 503A bulks list, and FDA's advisory committee has not voted on it yet.
Sport (WADA): Not named on the list, but as a substance with no approval for human use it falls under S0 (non-approved substances), which is prohibited at all times.
Your body controls how much it makes and where it goes. Too much in the wrong place is linked to psoriasis, rosacea and lupus-type inflammation.
The small first trial looked good, but the bigger follow-up found no overall benefit over placebo. Both put it on the skin; neither tested shots.
LL-37 is built to break open cell walls and pull in immune cells, so redness and soreness at the spot are common.
Last checked 2026-10