Diseases of the larynx itself such as acute laryngitis caused by a cold, compression by a tumour in the neck, trauma to the neck, compression of the laryngeal nerve by the thyroid gland or the adjacent tissue trachea can all cause hoarseness. In addition, hoarseness can also be caused by laryngeal oedema due to drug allergies, long-term inhalation of harmful gases or long-term incorrect pronunciation habits.