Limited human dataNot FDA approved

LL-37 side effects

Also known as: LL37 · LL 37 · Cathelicidin · Human cathelicidin antimicrobial peptide · CAP-18 · hCAP-18 fragment · Ropocamptide

Updated Oct 24, 202634 sources

9 side effects reported for LL-37: 2 from studies and labels, 7 from users and guides. 4 come with the ways people manage them.

LL-37 overview

Side effects reported in studies and labels

Rates as each trial or label states them. A rate from one trial does not carry over to research-grade vials or other doses.

From trials and regulators2

Clinical studies and regulatory documents.

Widespread skin eruption after intratumoral dosing
One published case from the melanoma trial; resolved within 2 months of stopping
Topical use in ulcer trials
No local or systemic safety concerns at 0.5 to 3.2 mg/mL; well tolerated at 0.5 and 1.6 mg/mL in 148 patients

Side effects users and guides report

What people post and what dosing guides list. These are reports, not measured rates.

From users and guides7

Community reports, competitor and vendor guides, media.

Injection-site redness, swelling, itching or burning
The most common report with subQ use; lasts 12 to 48 hours
How people manage it
- Inject slowly over 3 to 5 seconds
- Start at a lower amount
- Persistent or spreading reactions are a stop signal
Flushing or warmth near the site
Linked to LL-37 releasing histamine from mast cells
Flu-like symptoms with the first doses
Some users; usually fades with continued dosing, more often at higher doses
How people manage it
- Start lower and titrate up
Low-grade fever, fatigue and body aches in the first days
Commonly reported in forum aggregates, read by users as immune activation
Headache or mild fatigue
Less common
Herx-like flare
Less common; blamed on bacterial die-off as biofilms break up
How people manage it
- Start at 100 mcg and increase gradually
Psoriasis- or rosacea-like skin flare
Theoretical; guides treat new plaques or facial flushing as a reason to stop
How people manage it
- Stop and see a clinician

Who should avoid it, and what not to combine

Psoriasis, lupus or rosaceaCondition
LL-37 is tied to disease activity in all three: it turns self-DNA into an immune trigger and is raised in rosacea skin.
Mast cell activation syndromeCondition
One guide lists it as a strong relative contraindication; LL-37 releases histamine from mast cells.
Active or past cancerCondition
FDA cites nonclinical tumour promotion in some tissues; lab data show growth of lung cancer and melanoma cells.
Pregnancy or breastfeedingCondition
No safety data.

How much is known

Limited human data

Human data are topical or intratumoral only. A 34-person venous ulcer trial favoured the lowest strength; the 148-person Phase IIb missed overall, with a possible benefit in large ulcers. A diabetic foot ulcer cream trial improved granulation. A 4-person melanoma injection study exists. No subQ, oral or systemic trial found.