After 16 days of smoking cessation, systemic symptoms, respiratory symptoms and abnormal weight gain will mainly occur. Due to the differences in the body, the length of smoking time and the amount of cigarettes smoked, the symptoms shown by each person will be different. 1. Systemic symptoms: After 16 days of quitting smoking, patients may experience nicotine withdrawal syndrome, showing symptoms such as irritability, nervousness, anxiety, palpitations (rapid heartbeat, often accompanied by panic), chest tightness, mental weakness, and so on, which can be improved on their own after a period of time and gradual adaptation. 2. Respiratory symptoms: when quitting smoking, the damage to the respiratory system stops, the consumption of airway damage repair begins to decrease, sputum and other self-cleaning ability to enhance the ability to cough, cough sputum increase, some people may also appear to quit smoking sense of taste and sense of smell increase. 3. Abnormal weight gain: After quitting smoking, the consumption for repairing the damage caused by tobacco begins to decrease, and the energy to replenish the body increases, which may lead to abnormal weight gain, so when quitting smoking, diet should be controlled appropriately to avoid excessive weight gain. Patients need to persevere after the emergence of smoking cessation to avoid relapse, and in daily life, you can cultivate and develop your own interests to divert attention, and persevere through the period of smoking cessation.