If you do not have a cold, but you have a dry cough, you need to consider certain diseases, commonly some diseases of the respiratory system. If the cough lasts for a longer period of time, for example, six months or even more than a year, chronic inflammation of the airway or even an occupying lesion should be considered. Chronic inflammation includes tuberculosis caused by infection with Mycobacterium tuberculosis, chronic bronchitis and bronchiectasis caused by various factors. Occupying lesions include mainly bronchopulmonary carcinoma, alveolar cell carcinoma, and progressively enlarged benign tumors, including teratomas and malignant tumors. Inflammatory and occupying lesions can irritate the airways and cause the symptoms of dry cough.