Background. Asthma exacerbations are a common reason for Emergency Department (ED) visits in children. Aim. To analyze differences among age groups in terms of triggering factors and seasonality and to identify those with higher risk of severe exacerbations. Methods. We retrospectively revised the files of children admitted for acute asthma in 2016 in our Pediatric ED. Results. Visits for acute asthma were 603/23197 (2.6%). 76% of the patients were <6 years old and 24% ≥6. Infections were the main trigger of exacerbations in both groups; 33% of the school-aged children had a triggering allergic condition (versus 3% in <6 years; p<.01). 191 patients had a previous history of asthma; among them, 95 were ≥6 years, 67% of whom were not using any controller medication, showing a higher risk of a moderate-to-severe exacerbation than those under long-term therapy (p<.01). Exacerbations peaked in autumn and winter in preschoolers and in spring and early autumn in the school-aged children. Conclusions. Infections are the main trigger of acute asthma in children of any age, followed by allergy in the school-aged children. Efforts for an improved management of patients affected by chronic asthma might go through individualized action plans and possibly vaccinations and allergen-avoidance measures.