The purpose of this project is to evaluate in a randomized clinical trial, double-blind, controlled, the effects of a dietary supplement containing Lactobacillus reuteri DSM 17938 and vitamin D3 in reducing bronchial inflammation and improve asthma control in patients in children with mild / moderate persistent asthma .

To evaluate if the supplementation for three months with Lactobacillus reuteri DSM 17938 (108 CFU) + Vitamin D3 (400 IU) result in a reduction of the degree of allergic bronchial inflammation, measured with the Fractional exhaled nitric oxide (FeNO) and with a series of markers of bronchial inflammation (measured at 'beginning and at the end of the treatment on exhaled condensate): Interleukin 2(IL-2); Interleukin 4 (IL-4); Interleukin 10(IL-10); Interferon γ (IFN-γ).

Inclusion Criteria:

• Patients aged between 6 and 14 years old, of both sexes
• Diagnosis of mild / moderate persistent asthma (GINA step 2/3)
• Allergy mite (Dermatophagoides farinae and pteronyssinus + + + / + + + +)
• Levels of vitamin 25 (OH) D <30 ng / ml
• Signature of the informed consent of one parent or a legal representative

Exclusion Criteria:

• Cardiovascular disease or systemic
• anatomical abnormalities
• Other respiratory diseases
• Taking probiotics and / or prebiotics in the previous 2 weeks
• Taking vitamin D or systemic corticosteroids within 4 weeks
• Participation in other clinical trials