Children with allergic rhinitis had significantly reduced levels of the antimicrobial peptide LL-37 (cathelicidin) in their nasal fluid, with levels dropping further as disease severity increased.
2.3 vs. 2.6 ng/ml (p<0.001)Nasal fluid LL-37 levels were significantly lower in children with allergic rhinitis versus healthy controls, with even lower levels in moderate/severe disease
What the researchers found
Children with allergic rhinitis had significantly lower nasal fluid LL-37 levels than healthy controls (median 2.3 ng/ml vs. 2.6 ng/ml, p<0.001). The levels were further reduced in moderate/severe AR compared to mild AR (2.2 ng/ml vs. 2.5 ng/ml, p<0.001). All AR patients were newly diagnosed and medication-free, eliminating treatment as a confounding factor.
Why it matters
Allergic rhinitis affects millions of children worldwide, and current treatments focus on symptom management rather than addressing underlying immune mechanisms. The finding that cathelicidin levels correlate inversely with disease severity suggests this antimicrobial peptide may have immunoregulatory functions in allergic inflammation. This could open new avenues for biomarker development (using LL-37 levels to assess severity) or therapeutic approaches that boost cathelicidin to modulate the allergic response.
How the study worked
This case-control study enrolled 46 children newly diagnosed with allergic rhinitis (medication-naive) and 33 healthy controls. Nasal secretions were collected using polyurethane sponge nasal secretion collectors, and LL-37 peptide levels were measured using ELISA (enzyme-linked immunosorbent assay). Disease severity was classified to compare LL-37 levels between mild and moderate/severe groups.
What this study cannot tell us
This is a cross-sectional observational study, so it cannot determine whether low LL-37 causes allergic rhinitis or is a consequence of it. The sample size is modest (79 total children). The absolute differences in LL-37 levels, while statistically significant, are relatively small. The study did not measure other inflammatory markers or immune mediators that could help explain the mechanism. Nasal fluid collection methods can introduce variability.
How to read the evidence
This is a case-control observational study in children with a modest sample size (79 total). While the statistical significance is strong (p<0.001), the cross-sectional design cannot establish causality, and the findings need replication in larger cohorts.
When this study was published
Published in 2016, this study is about 10 years old. The connection between antimicrobial peptides and allergic disease has continued to be explored since then, but the core findings about LL-37 levels in allergic rhinitis remain relevant.
The bigger picture
This study contributes to a growing body of research showing that antimicrobial peptides like cathelicidin do much more than fight infections. Their immunoregulatory roles in allergic and inflammatory diseases are increasingly recognized. Understanding how innate immune peptides interact with allergic pathways could reshape how we think about and treat conditions like allergic rhinitis, asthma, and atopic dermatitis — moving from symptom suppression toward immune system rebalancing.
Questions still open
- Does low nasal LL-37 contribute to the development of allergic rhinitis, or is it a downstream effect of allergic inflammation?
- Could boosting cathelicidin levels in the nasal cavity — through supplementation or vitamin D (which induces cathelicidin expression) — help treat or prevent allergic rhinitis?
- Do children with allergic rhinitis also have reduced cathelicidin levels in other mucosal sites, suggesting a systemic innate immune deficit?
Common questions
What is LL-37 and what does it normally do in the nose?
Could vitamin D help with allergic rhinitis through cathelicidin?
Read the original research
Beyond anti-microbial properties: The role of cathelicidin in allergic rhinitis.
Allergologia et immunopathologia, 44(4), 297-302
Citation
Dilek, F; Gultepe, B; Ozkaya, E; Yazici, M; Gedik, A H; Cakir, E. (2016). Beyond anti-microbial properties: The role of cathelicidin in allergic rhinitis.. Allergologia et immunopathologia, 44(4), 297-302. https://doi.org/10.1016/j.aller.2015.07.006