What is an adverse drug reaction? China’s “Measures for Reporting and Monitoring Adverse Drug Reactions” states that an adverse drug reaction is a harmful reaction to a qualified drug that occurs under normal dosage and is unrelated to the purpose of the drug or is unexpected. Why do adverse reactions occur? On the one hand, it is the factor of the drug itself, and on the other hand, it is the factor of the patient. The active ingredients, additives, and excipient materials of a drug can trigger adverse reactions. If a patient is allergic to a particular drug, there may be cross-allergy to the same class of drugs with similar chemical structure, and the patient should make special instructions to the doctor when seeking medical treatment to avoid the occurrence of adverse reactions. In addition, adverse reactions can be triggered by improper administration of medications. Intravenous drug administration accounts for more than half of the reported adverse reactions. How can patients judge? How can patients determine whether an adverse reaction has occurred after the drug has been administered? In fact, an adverse reaction occurs whenever there is an abnormal discomfort that is different from the manifestation of the disease itself before treatment. For example, if nausea, vomiting, abdominal pain, diarrhea and other symptoms occur after taking cold medicine, we should consider whether there is an adverse reaction if food-borne factors are excluded. In addition, patients can carefully read the drug instructions to see if there are statements that match their situation. When it is difficult to judge by yourself, it is recommended to consult your doctor or pharmacist in time. What should I do? What should patients do when an adverse drug reaction occurs? Once the occurrence of physical discomfort different from the original disease, all drugs should be discontinued immediately. Most adverse reactions with mild symptoms can recover on their own after stopping the drug. For more serious adverse reactions, or if the patient has a chronic disease and cannot stop the drug at will, the patient must go to the hospital and consult a doctor for help. More serious adverse drug reactions may require hospitalization. Irrational clinical use of drugs, especially the irrational use of antibacterial drugs is relatively common, and the widespread use of a large number of broad-spectrum antibiotics has led to two serious consequences: one is the generation of bacterial resistance, and the other is the triggering of various adverse reactions. In response to the current situation, the author makes the following recommendations: First, the use of antibacterial drugs should have strict indications. Secondly, the long-term use of broad-spectrum or simultaneous use of multiple antibiotics is not advisable. Again, there should be clear indications for the combined application of antibacterial drugs, and infections that can be effectively treated with a single drug should not be combined as much as possible.