Quit-smoking syndrome is a series of symptoms that occur after a smoker suddenly quits smoking. The most common and serious symptoms are the following: First, sleep disruption. This is something that makes quitting smoking more painful and makes it difficult to fall asleep. Second, coughing. Because of the large amount of mucus produced after years of smoking, mucus is loosened from the respiratory tract during quitting smoking, resulting in coughing, coughing up phlegm, and constipation. Third, headache. Some of them can last for 1 day and may recur after 1 week. Fourth, there will be a feeling of hunger. Many smokers have a big appetite after quitting, and in order to avoid this situation weight gain, may engage in some physical exercise. Fifth, the hands and fingertips to tremor can last for several weeks. Others such as poor concentration, sore scalp, itchy hands and feet, and night sweats are also relatively common.