Chronic cough affects 8-10% of adults. The prevalence of cough in the community is about 2.3-18% of adult people. The range of chronic cough in respiratory clinics is 10-38%. A meta-analysis found that the prevalence of chronic cough in the general population (defined as cough lasting longer than three months) was 9.6%. Cough was more common in Europe (12.7%), Oceania (18.1%) and the United States (11%) compared to Asia (4.4%) and Africa (2.3%). The definition of chronic cough varied across studies. Cough was more common in patients with cough than in non-smokers, and the prevalence of cough increased with the average annual concentration of nitrogen dioxide, total suspended particulate matter, and atmospheric concentrations of particles less than 10 μ in diameter. Surveys have shown that the average duration of cough is 6.5 years. 60% of patients have persistent symptoms despite treatment. 1. Definition of chronic persistent cough Cough is a reflex activity, some of which can be controlled by the will. Cough is one of the symptoms of many common respiratory diseases and can present as acute (within three weeks), subacute (three to eight weeks), or chronic (more than eight weeks). The guidelines state that 0-46% of patients have persistent cough despite evaluation and treatment of their condition. This condition is referred to as chronic persistent cough (CRC), chronic idiopathic cough, or unexplained chronic cough. Since patients with unexplained chronic cough often receive specific treatments, such as inhaled glucocorticoids or proton pump inhibitors, they can also be classified as having a chronic intractable cough. 2. Cough hypersensitivity syndrome Cough hypersensitivity syndrome is associated with hypersensitivity reactions in the larynx and upper airways. It is considered as a sensory airway neurological disease caused by hypersensitivity to harmless irritants and is mainly caused by mucosal upregulation of the cough receptors transient receptor potential V1 (TRPV1) and TRPA1. The causes of chronic cough such as asthma, sinusitis, and gastroesophageal reflux disease (GERD) are considered to be different phenotypes of the syndrome. CRC is considered to be a phenotype of cough hypersensitivity syndrome; although the contributing factors are unknown, it is assumed to be caused by GERD. The concept of cough hypersensitivity syndrome has certain advantages. It may explain why only a subset of the population is associated with diseases of asthma, sinusitis, and gastroesophageal reflux, while others cough unrelated to disease. It explains why cough tends to be refractory and why it may present without other diseases. It is also consistent with CRC often appearing after upper respiratory tract infections. Most of the evidence supporting cough hypersensitivity syndrome is based on expert opinion, which is its limitation, and an objective method for determining cough hypersensitivity syndrome has neither been recommended nor agreed upon. Furthermore, it has not been established that the concept of cough hypersensitivity can be the origin of other symptoms, such as laryngeal symptoms and fatigue, often coexisting in patients with chronic cough. 3. Laryngeal hypersensitivity Laryngeal hypersensitivity is another new concept that contributes to the understanding of CRC. It is defined as an increased sensitivity of the larynx to harmless stimuli causing abnormal laryngeal sensory symptoms including cough, dyspnea, hoarseness or laryngospasm. Although some features of CRC are part of the cough hypersensitivity syndrome, many patients have symptoms that are limited to the larynx. Laryngeal hypersensitivity syndrome may be a useful concept that defines a sensory abnormality. This sensation (abnormal laryngeal sensation) is critical and may be more troublesome for many patients than the cough itself. The Laryngeal Hypersensitivity Questionnaire can be used to measure the laryngeal hypersensitivity response. The questionnaire is validated, reproducible, and responsive and consists of 14 items divided into pain, caloric meter items, irritation, and obstruction. The cutoff score for normal function is 17.1 and the minimal difference is 1.3 points. Cough hypersensitivity syndrome may overlap with other laryngeal hypersensitivity syndromes. Cough hypersensitivity reactions can be triggered in the lower respiratory tract and also in the larynx, as part of laryngeal hypersensitivity. In addition, laryngeal hypersensitivity reactions are characterized by paradoxical vocal fold movement (PVFM), hysterical bulbarism, and muscle tension vocal disturbances. In patients with cough hypersensitivity syndrome and laryngeal hypersensitivity syndrome, several associated disorders can act as triggers. These diseases are gastroesophageal reflux disease, sinusitis, use of angiotensin-converting enzyme 1 inhibitors, asthma, and non-asthmatic eosinophilia. Further research on the concept of cough hypersensitivity syndrome is needed in the future, including understanding the mechanisms, diagnosis, and treatment of its associated laryngeal hypersensitivity syndrome.