LL-37 has real, evidence-based potential to help with eczema. The core problem in eczema is a defective skin barrier + excessive Staphylococcus aureus colonization that fuels flares. Multiple studies show LL-37 is often deficient or insufficiently produced in eczematous skin, which directly contributes to that vulnerability. Key Evidence - • A major 2002 NEJM study (highly cited) biopsied skin from atopic dermatitis patients and found markedly lower LL-37 (and human β-defensin 2) in both acute and chronic lesions compared to psoriasis lesions or normal skin. Psoriatic skin ramps up LL-37 aggressively; AD skin does not. This deficiency explained the high S. aureus loads (up to 10^7 CFU/cm²) in inflamed AD skin. The combination of LL-37 + defensins normally kills S. aureus synergistically — levels in AD skin were too low to do the job effectively. Th2 cytokines (IL-4, IL-13) that dominate eczema actively suppress these peptides. • A 2009 study in adults with atopic eczema found LL-37 upregulated in lesional skin versus non-lesional skin in the same patients (statistically significant), and it was consistently present around areas of epidermal injury or vesicles. Researchers interpreted this as LL-37 participating in the skin’s attempt at re-epithelialization and repair. However, overall levels still appear inadequate compared to what’s needed or what other inflammatory skin diseases achieve. • Later work (including a 2023 analysis) confirmed LL-37 as one of the few antimicrobial peptides consistently impaired in both non-lesional and lesional AD skin, underscoring its specific role in the disease process. • LL-37 also shows direct antiviral effects (e.g., against HSV-2) and is lower in AD patients who develop eczema herpeticum, a nasty complication. Mechanistically LL-37 isn’t just an antibiotic — it’s multifunctional: • Kills and disrupts S. aureus (including biofilm-forming strains common in chronic eczema). • Promotes skin repair: Stimulates keratinocyte migration, proliferation, and wound closure (antibodies blocking LL-37 slow re-epithelialization in models).

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