The etiology of cough is often the result of a combination of many complex factors, mainly the following: 1. Inhalants Inhalants are classified into two types: specific and non-specific. The former are dust mites, pollen, smoke, fungi, animal dander, etc.; non-specific inhalants such as sulfuric acid, sulfur dioxide, chlorine ammonia, etc. The specific inhalants for occupational cough are such as toluene diisocyanate, phthalic anhydride, ethylenediamine, penicillin, protease, amylase, silk, animal dander or excrement, etc. In addition, the non-specific ones are formaldehyde and formic acid, etc. 2. Infection The formation and onset of cough is associated with recurrent whistling infections. In patients with cough, specific IgE for bacteria, viruses, mycoplasma, etc. can be present and can stimulate coughing if the corresponding antigens are inhaled. After viral infection, direct damage to the epithelium of the whistle tract can occur, resulting in increased whistle tract reactivity. It has been suggested that histamine release from basophils is increased by interferon and IL-1 produced by viral infection. In the lactation period, there are also many cases of coughing after infection with whistling viruses (especially whistling syncytial virus). Cough caused by parasites such as roundworms and hookworms can be seen in areas with poor hygiene. Cough attacks due to diet are often seen in cough patients, especially in infants and children who are prone to food allergies, but this decreases with age. The most common foods that cause allergies are fish, shrimps and crabs, eggs, milk, etc. 4. Climate change Cough can be triggered by changes in temperature, air pressure and/or ions in the air, so it is more common in the cold season or in autumn and winter when the climate changes. 5. Mental factors Patients’ emotional excitement, nervousness and anger can trigger coughing episodes, which are generally thought to be caused by cortical and vagal reflexes or hyperventilation. 6. Exercise In 70% to 80% of cough patients, cough is induced after strenuous exercise, called exercise-induced cough, or exercise cough. Clinical manifestations include cough, chest tightness, shortness of breath, and wheezing, and croup can be heard on auscultation. In some patients, although there is no typical asthma manifestation after exercise, bronchospasm can be detected by pulmonary function measurements before and after exercise. Cough and medications Some medications can cause coughing episodes, such as the cough caused by blocking beta2-adrenergic receptors. Smoking is harmful to health, it is common knowledge that everyone knows, the specific hazards of smoking are the following four points: First, the carbon monoxide and nicotine in tobacco mist can make the tissue and myocardial hypoxia, inducing coronary spasm, increased blood viscosity, interference with lipid metabolism, and promote the deposition of cholesterol-like substances. Second, the endothelial cells that can maintain the normal function of the arterial wall have a damaging effect, so that the heart rate and cardiac output increases, but also can prompt vasoconstriction and increase blood pressure, these all make the heart burden increased, long-term smoking can reduce the coronary vasodilator function, increase platelet aggregation, increase the blood fibrinogen, which leads to and aggravate the formation of coronary atheroma plaque. Third, smoking changes the composition of blood lipids, reducing high-density lipoprotein, increasing low-density lipoprotein, and reducing serum antioxidants, which promotes the occurrence and development of atherosclerosis and coronary artery disease. Fourth, for some younger patients, excessive smoking is a key factor in the development of acute myocardial infarction. Fifth, studies have shown that smokers have about 2.2 times the risk of coronary heart disease as non-smokers, and that smoking more than doubles people’s chances of developing heart disease. Therefore, patients with coronary heart disease must resolutely quit smoking.