Chronic Postnasal Drip (Upper Airway Secretion Syndrome): This is a common cause of chronic cough, especially when the cough is dry (without mucous production). The lack of fever and other symptoms supports this diagnosis, as postnasal drip can cause irritation leading to cough without systemic symptoms.

Asthma: Even without wheezing, asthma can present with a chronic cough as the sole symptom, known as cough-variant asthma. The absence of fever and mucous production does not rule out asthma.
Gastroesophageal Reflux Disease (GERD): GERD can cause a chronic cough due to the reflux of stomach contents into the esophagus, irritating the throat and triggering cough. The lack of other symptoms like heartburn does not exclude GERD as a cause.
Allergic Rhinitis: Similar to postnasal drip, allergic rhinitis can cause chronic cough through the same mechanism of upper airway irritation, even in the absence of noticeable allergic symptoms.

Lung Cancer: Although less likely in the absence of other symptoms like weight loss, hemoptysis, or systemic symptoms, lung cancer can present with a chronic cough as an early symptom. It's crucial to consider this, especially in smokers or those with a significant smoking history.
Tuberculosis (TB): TB can cause a chronic cough, often without significant mucous production initially. The absence of fever does not rule out TB, especially in individuals who have been exposed or are from endemic areas.
Pulmonary Embolism: While typically presenting acutely, in some cases, a pulmonary embolism can cause a chronic cough, especially if it's a small, recurrent, or unresolved embolism. This diagnosis is critical to consider due to its high mortality if untreated.

Sarcoidosis: A systemic disease that can affect the lungs, causing a chronic cough among other symptoms. It's less common but should be considered in the differential, especially if other symptoms like skin lesions or eye involvement are present.
Eosinophilic Pneumonia: A rare condition characterized by an accumulation of eosinophils in the lungs, which can cause a chronic cough. It's often associated with other symptoms like fever and weight loss, but these can be absent in some cases.
Histiocytosis X (Langerhans Cell Histiocytosis): A rare disorder that can affect the lungs and cause a chronic cough, among other respiratory and systemic symptoms. It's more common in smokers and can mimic other lung diseases.