People with atopic eczema have more of the natural skin peptide LL‑37 in the itchy, inflamed patches than in the unaffected skin, but the amount doesn't track with how bad the eczema is. Healthy skin and the non‑itchy areas of eczema patients have similar LL‑37 levels. The peptide shows up whenever the skin is damaged, hinting it may help with wound healing.

Atopic eczema (AE) is a common multifactorial chronic skin disease associated with a defective skin barrier and increased susceptibility to skin infections. The human cathelicidin LL-37 plays a role in the host defence of skin. Studies have demonstrated deficient expression of LL-37 in skin of AE patients. The aim of this study was to investigate the expression of LL-37 in lesional skin compared with nonlesional skin in patients with different severity of AE, patients with other eczema and healthy subjects. Twenty patients with AE, four patients with other eczema and 10 healthy subjects were included. Severity of AE was graded using SCORing of atopic dermatitis (SCORAD). Skin biopsies were taken from lesional and nonlesional skin from all patients and from skin of healthy controls. The levels of LL-37 mRNA were analysed by quantitative reverse transcriptase-polymerase chain reaction. Evaluation of dermal and epidermal protein expression of LL-37 and the degree of inflammation was performed by immunohistochemical stainings. Patients with AE and patients with other eczema had significantly (P < 0.05) higher levels of LL-37 in lesional skin than in nonlesional skin. The expression of LL-37 was not statistically associated to severity of AE valued by SCORAD. Nonlesional skin from patients did not differ from skin of healthy subjects in terms of LL-37 expression. In the presence of epidermal injury or vesicles the LL-37 peptide was always detected. Patients with AE exhibit enhanced expression of LL-37 in lesional skin compared with nonlesional, suggesting a role of LL-37 in AE that might be associated with the process of re-epithelialization.