Asthma: This is a common condition in children that can cause chronic cough, especially at night, and can be productive. The cough in asthma is often associated with wheezing and shortness of breath, but in young children, the presentation can be atypical, with cough being the predominant symptom.

Reactive Airway Disease: Similar to asthma, but the airway hyperreactivity is not as persistent or severe. It can cause cough, especially at night, in response to various triggers.
Bronchiolitis: Although typically seen in younger infants, bronchiolitis can occur in older infants and toddlers, especially during respiratory syncytial virus (RSV) season, causing a persistent cough.
Allergic Rhinitis: Postnasal drip from allergic rhinitis can cause a chronic cough, which may be more noticeable at night.
Gastroesophageal Reflux Disease (GERD): Stomach acid reflux can irritate the throat and cause a cough, which may worsen at night when the child is lying down.

Pertussis (Whooping Cough): Although vaccination has reduced its incidence, pertussis can still occur, especially in areas with low vaccination rates or in children who have not completed their vaccination series. It's characterized by a severe, persistent cough that can be productive and is often accompanied by a distinctive whoop sound.
Tuberculosis (TB): A chronic cough in a child, especially if exposed to someone with TB, requires investigation for this potentially deadly disease.
Foreign Body Aspiration: If the cough started suddenly, a foreign body in the airway should be considered, as it can cause a persistent cough and potentially life-threatening complications if not removed.
Congenital Heart Disease: Severe, uncorrected congenital heart defects can lead to pulmonary congestion and a chronic cough.

Cystic Fibrosis: A genetic disorder that leads to the production of thick, sticky mucus, causing chronic respiratory and digestive problems, including a persistent, productive cough.
Primary Ciliary Dyskinesia (Kartagener Syndrome): A rare genetic disorder affecting the cilia, leading to chronic respiratory infections and a persistent cough.
Interstitial Lung Disease: A broad category of rare lung disorders that can cause chronic cough among other symptoms.