Children with mild to moderate asthma exacerbation will be given the first dose of salbutamol and will be reassessed after 20 min by the emergency department attending. If further salbutamol is needed, subjects automatically will receive the second dose 20 min apart and receive either single dose of intramuscular dexamethasone (0.6 mg/kg to a maximum of 18 mg) or oral prednisolone for 3 days (1 mg/kg to a maximum of 40 mg), given orally .