Allergic Rhinitis: This condition is characterized by symptoms such as cough, runny nose, and sneezing, which can persist for more than a month, especially if the individual is continuously exposed to the allergen. The chronic nature of the symptoms and the presence of a runny nose point towards an allergic cause.

Chronic Sinusitis: This condition often presents with persistent nasal congestion, runny nose, and cough, which can last for more than a month. It is usually caused by bacterial or fungal infections and can be a complication of acute sinusitis.
Asthma: Although primarily known for causing wheezing and shortness of breath, asthma can also present with a chronic cough. In some cases, especially in children, the primary symptom might be a cough, and the presence of a runny nose could be due to concomitant allergic rhinitis.
Gastroesophageal Reflux Disease (GERD): GERD can cause a chronic cough due to the reflux of stomach contents into the esophagus, irritating the throat and lungs. A runny nose might not be a direct symptom but could be related to the overall discomfort and clearing of the throat.

Tuberculosis (TB): Although less common in some regions, TB is a critical diagnosis not to miss due to its serious implications and the need for prompt treatment. A chronic cough lasting more than a month is a key symptom, and while a runny nose is not typical, it could be present in the context of pulmonary TB affecting the upper respiratory tract.
Lung Cancer: A persistent cough is one of the early symptoms of lung cancer. While a runny nose is not a typical symptom, it could be part of a broader symptom complex, especially if the cancer affects the upper respiratory tract or causes secondary infections.
Immunodeficiency: Conditions that impair the immune system, such as HIV/AIDS, can lead to chronic and recurrent infections, including those causing cough and runny nose. Identifying an underlying immunodeficiency is crucial for appropriate management.

Cystic Fibrosis: This genetic disorder leads to the production of thick, sticky mucus that can cause respiratory and digestive problems. While more commonly diagnosed in childhood, some milder forms might not be identified until later in life, presenting with chronic respiratory symptoms.
Sarcoidosis: A condition characterized by the growth of granulomas (inflammatory cells) in various parts of the body, including the lungs. It can cause a chronic cough and, less commonly, upper respiratory symptoms like a runny nose.
Eosinophilic Granulomatosis with Polyangiitis (Churg-Strauss Syndrome): A rare autoimmune condition that can cause asthma, high levels of eosinophils, and vasculitis (inflammation of blood vessels), leading to a variety of symptoms including cough and runny nose.