Background Our group recently reported a randomized and placebo-controlled clinical trial on the efficacy of a twice-daily concoction of five herbal ingredients (Pentaherbs formulation, PHF) in treating children with atopic dermatitis (AD).

Objectives To investigate the immunomodulatory effects that may be induced by PHF treatment.

Methods We investigated the effects of PHF on cytotoxicity and proliferation of phytohaemagglutinin (PHA)- and staphylococcal enterotoxin B (SEB)-stimulated peripheral blood mononuclear cells (PBMC) isolated from buffy coat of blood donors. PHF-induced immunomodulation for five inflammatory mediators in cultured PBMC was measured by reverse transcription–polymerase chain reaction and enzyme-linked immunosorbent assay. The effects of a 3-month, open-label study of PHF on circulating inflammatory mediators in children with AD were also assessed.

Results PHF at up to 1 mg mL⁻¹ dose-dependently suppressed PBMC proliferation. The addition of PHF to cultured PBMC reduced supernatant concentrations of brain-derived neurotrophic factor (BDNF), interferon (IFN)-γ and tumour necrosis factor (TNF)-α in response to PHA, and BDNF and thymus and activation-regulated chemokine (TARC) following SEB stimulation. PHF increased epithelial cell-derived neutrophil activating peptide-78 levels in culture supernatants. At the RNA level, PHF suppressed the transcription of BDNF, TARC, IFN-γ and TNF-α. Twenty-eight children with AD were treated with PHF for 3 months, and their mean plasma concentrations of BDNF and TARC decreased significantly from 1798 pg mL⁻¹ and 824 pg mL⁻¹ at baseline to 1378 pg mL⁻¹ and 492 pg mL⁻¹ (P = 0·002 and 0·013, respectively) upon study completion.

Conclusions PHF possesses in vitro and in vivo immunomodulatory properties that may mediate the clinical efficacy observed in AD treatment.