My 21-month-old child has a severe cough, mostly during night when she's asleep, sometimes difficulty breathing at the end. what could be the problem?

New or chronic: If this is a chronic problem, she could have asthma or reflux or a number of other respiratory conditions. If it is new and she is making a sharp inhaling sound after a cough bout she could have pertussis or a pertussis like illness. Has she been vaccinated? If her breathing difficulty is not a characteristic sharp inhale with a whoop, she may, again have cough variant asthma, bronchitis,or a viral respiratory illness that needs to run it’s course. Use cool humidified air for comfort, allow her to drink a warm juice with honey to help suppress the cough, smash some cough drops and let her suck on small pieces, and if she is not better in a few days bring her in to her doctor.