Immune

LL-37 (cathelicidin)

The body's own antimicrobial peptide, studied for wound healing and infection; a research compound, not a treatment.

Limited evidenceNot approvedAdd to compare

What it is

LL-37 is a 37-amino-acid peptide from the cathelicidin family — part of the innate immune system's first line of defence. It is found in human skin, gut lining and immune cells, and it kills microbes directly while also signalling to immune cells. Synthetic LL-37 is sold as a research peptide for wound and infection research; it is not an approved medicine.

How it works

1
Forms pores in bacterial membranes, killing a broad range of organisms — a different strategy from antibiotics.
2
Acts as a chemotactic signal, drawing immune cells to a site of injury.
3
Binds bacterial lipopolysaccharide and dampens the inflammatory response it triggers.
4
Stimulates blood-vessel growth and cell migration in wound-healing models.
5
Can be pro-inflammatory at higher concentrations, which complicates its use as a therapy.

What it's studied for

Wound healing and skin infection models

Chronic leg ulcer research

Innate immune response studies

Rosacea and inflammatory skin conditions (research)

Reported and studied effects

Antimicrobial killing of bacteria in laboratory studies
Wound-healing acceleration in animal models
Reduced inflammation in some models, increased in others
Reported skin irritation with topical use

Research protocol notes

Research context only

Research context only — no approved protocol exists. Laboratory work uses microgram-per-millilitre concentrations in cell culture, and animal studies use local or systemic doses. Human trial experience is limited to topical and small infusion studies without a standardised dose; any injected regimen sold online is untested territory.

These figures are described so you can understand what researchers did. They are not a dose, a schedule, or a suggestion — and they are not a substitute for a doctor.

Possible side effects and contraindications

Safety profile

Possible side effects

Injection-site or application-site irritation
Possible worsening of inflammation in some conditions
Cytotoxicity at high concentrations in laboratory studies
Long-term safety unknown

Contraindications and cautions

Not established
Pregnancy, breastfeeding and childhood
Autoimmune disease without specialist advice
Competitive athletes should check anti-doping rules

A side-effect list is never complete, and these are not the only situations that warrant caution. Anything unexpected, or anything you are unsure about, should be discussed with a doctor before use.

Evidence assessment

Limited evidenceSmall human studies or animal data only

Small human studies or animal data only

Its antimicrobial and immune roles are well characterised in the laboratory, but human trials of LL-37 as a therapy are few and small, and no product is approved.

References

References link to published literature, regulator pages or literature indexes. Where a link points to a search, it collects the peer-reviewed work on that molecule rather than a single study.

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