Oral Lactobacillus rhamnosus GG ingestion for 5 days to 4 weeks has been shown to alleviate clinical symptoms of gastrointestinal inflammation and atopic dermatitis. To determine whether oral Lactobacillus rhamnosus GG may act by generating immunosuppressive mediator in atopic children. Lactobacillus rhamnosus GG (ATCC 53103) at a daily dose of 2 x 1010 cfu was added for 4 weeks to the diets of nine children (mean age, 21 months) with atopic dermatitis. Blood and faecal samples were collected before supplementation and at early (2 weeks) and late stage (4 and 8 weeks from the beginning). The concentrations of interleukin-6 (IL-6), IL-10, IL-12, tumour necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) in sera, as well as the production of IL-2, IL-4, IL-10 and IFNgamma in mitogen-induced peripheral blood mononuclear cells, were assessed. Secretory IgA and TNFalpha were also determined in faeces. The serum IL-10 concentration differed significantly between before, early and late samples (P < 0.001) due to the elevation of serum IL-10 in the later phase of oral Lactobacillus rhamnosus GG ingestion. The enhancement of IL-10 production in mitogen-induced cultures preceded the rise in serum IL-10. The enhanced IL-10 generation in vivo substantiates the anti-inflammatory properties of specific probiotic bacteria strains, and provides an additional reason for considering such treatments for patients with intestinal inflammation.