Beneficial effects of probiotics are long known to mankind. Research is beginning to unravel the true nature of the human microbiome and its interaction with the immune system. The growing prevalence of atopic diseases in the developed world led to the proposition of the “hygiene hypothesis.” Dysbiosis is linked to atopic diseases ; probiotic supplementation is able to alter the microbiome and certain probiotic strains have immunomodulatory effects in favor of a suppression of Th-2 and stimulation of a Th1 profile. To determine whether daily supplementation with specific Lactobacillus gasseri for 8 weeks can improve the clinical symptoms and immunoregulatory changes in school children suffering from asthma and allergic rhinitis (AR). We conducted a randomized, double-blind, placebo-controlled study on school children (age, 6－12 years) with asthma and AR. Our results showed the pulmonary function and peak expiratory flow rate increased significantly, and the clinical symptom scores for asthma and AR decreased in the probiotic-treated patients as compared to the controls. Further, there was a significant reduction in the TNF-α, IFN-γ, IL-12, and IL-13 production by the PBMCs following the probiotic treatment. In conclusion, probiotic supplementation may have clinical benefits for school children suffering from allergic airway diseases such as asthma and AR. In the mice model of mite-sensitive allergic asthma, oral administration with L. gasseri can attenuate major characteristics of allergen-induced airway inflammation and IL-17 pro-inflammatory immune response in a mouse model of allergic asthma, which may have clinical implication in the preventive or therapeutic potential in allergic asthma. Moreover, we found the immmuno-regulatory effect of L. gasseri in HDM-induced airway inflammation is through activation of PPARγ in dendritic cells. Hence, using probiotics as complementary treatment options in atopic dermatitis and food allergies seems to be a promising concept although the evidence is of a preliminary nature to date and more convincing trials are needed.