Inclusion Criteria:  Age greater than 1 year and less than 3 years Diagnosis of asthma by a pediatrician Parental consent Affiliation to the social security system  Exclusion Criteria:  Chronic pathologies: congenital heart disease, immune deficiency, cystic fibrosis, bronchopulmonary dysplasia, encephalopathy, primary ciliary dyskinesia, laryngomalacia, digestive pathology requiring digestive surgery Premature < 34 SA Recent antibiotic therapy (< 7 days) Treatment with oral corticosteroid therapy within the previous 10 days. Patient whose parent(s) is (are) minor(s)