Viral Upper Respiratory Tract Infection (URTI): This is the most common cause of nasal congestion and cough, often resulting from viruses such as rhinovirus, coronavirus, or influenza. The symptoms typically include runny nose, sneezing, cough, and sometimes fever.

Allergic Rhinitis: This condition is characterized by an allergic reaction to airborne allergens like pollen, dust mites, or pet dander, leading to nasal congestion, sneezing, runny nose, and cough.
Acute Sinusitis: Inflammation of the sinuses can cause nasal congestion, facial pain, cough, and sometimes fever. It can be viral or bacterial in origin.
Asthma: Although primarily known for causing wheezing and shortness of breath, asthma can also present with cough and may be exacerbated by upper respiratory infections or allergens.

Pneumonia: While less common than URTI, pneumonia is a serious condition that can present with cough and may be accompanied by fever, chest pain, and difficulty breathing. It requires prompt antibiotic treatment.
Pertussis (Whooping Cough): A highly contagious bacterial infection that can cause severe coughing fits, often accompanied by a characteristic "whoop" sound. It's particularly dangerous in infants and those with weakened immune systems.
Foreign Body Aspiration: Especially in children, the possibility of a foreign body (like a peanut or toy) being lodged in the airway should be considered, as it can cause sudden onset of cough and respiratory distress.

Cystic Fibrosis: A genetic disorder that affects the lungs, pancreas, and other organs, causing severe damage due to very thick, sticky mucus that clogs the airways and traps bacteria, leading to recurrent respiratory infections, cough, and nasal congestion.
Wegener's Granulomatosis (Granulomatosis with Polyangiitis): A rare autoimmune disorder that can cause inflammation of the blood vessels, leading to symptoms such as cough, nasal congestion, and potentially life-threatening complications if not treated.
Tuberculosis (TB): A bacterial infection that primarily affects the lungs but can spread to other parts of the body. It can cause cough, chest pain, and coughing up blood, among other symptoms. TB is less common in some regions but remains a significant concern globally.