Both medications serve different purposes. The prescribed oral medication (montelukast) is generally more effective for a seasonal allergic cough because it directly treats the underlying allergy and reduces airway inflammation. The inhaler you are using contains levosalbutamol, which is a quick-relief medicine designed to open the airways during sudden wheezing or shortness of breath, rather than treating a standard seasonal cough. You should switch to the prescribed oral medication as directed by your doctor. Only use the inhaler if your relative experiences active wheezing or difficulty breathing, and consult their doctor before combining treatments.