The double-edged sword of innate immunity — a natural antibiotic that, dysregulated, drives inflammatory disease. LL-37 is unusual in this register: it's sold as a healing/antimicrobial peptide, yet its largest and strongest evidence base is about its role in causing skin disease (rosacea, psoriasis
LL-37 is the body's own broad-spectrum antimicrobial peptide — the only human cathelicidin — a 37-amino-acid innate-immune effector made by skin and immune cells, switched on by vitamin D and injury, and activated by protease cleavage. It genuinely kills microbes (by disrupting their membranes) and supports wound healing and angiogenesis. But its defining feature is a dual role: it's also an "alarmin," and when its expression or processing goes wrong, it becomes a driver of inflammatory and autoimmune disease — it generates the inflammatory fragments of rosacea, breaks tolerance to self-DNA in psoriasis (via TLR9), and feeds lupus. That's the paradox for a register: LL-37 is sold as a healing/antimicrobial peptide, but its largest, most rigorous evidence base is about how it causes skin disease when dysregulated. As an exogenous therapeutic it's preclinical with no approvals, and administering a pro-inflammatory alarmin — particularly to anyone prone to rosacea or psoriasis — could plausibly do the opposite of healing. A fascinating, important molecule; a genuinely double-edged one; not a validated therapy.
not an approved drug; investigational. Not an approved cosmetic ingredient (an injectable pro-inflammatory alarmin is not a topical cosmetic). No compounding pathway.
An honest grade per outcome — drawn from the evidence, not any catalogue. Hype and undemonstrated marketing claims grade low.
A credentialed reviewer (PharmD / PhD / MD) will be named before this entry is finalised. Until then, treat it as a working draft. Last updated July 2026 (watch: engineered LL-37 analogs/fragments that dissociate antimicrobial from pro-inflammatory activity — the field's key therapeutic goal).
Grades reflect the published evidence, not our interest. No dosing, reconstitution, or administration is published for research compounds — that restraint is deliberate.
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