In addition to the therapeutic effect of the drug, sometimes there are some adverse reactions, the common ones are as follows: 1, allergic reactions: is some special physique (generally known as allergic body) of patients with some special reactions to the drug. Most commonly seen in antimicrobial and biological products, such as penicillin, streptomycin, gentamicin, chloramphenicol, etc.; biological products, such as tetanus antitoxin, various vaccines, etc.. When allergic reactions occur, rash and drug fever may occur in mild cases, and shock and even death may occur in severe cases. Therefore, in the use of some drugs that can cause allergic reactions must be allergy testing. 2, side effects: that is, other than the therapeutic effects. For example, when treating gastrointestinal spasmodic abdominal pain with atropine, dry mouth and blurred vision can occur; when treating urticaria with fenagin, patients appear drowsy and weak. It is difficult to avoid these side effects because they occur simultaneously with the therapeutic effect when applied in common doses.3. Toxic reactions: are harmful reactions to the human body that occur when the dose of the drug is too large or the duration of the drug is too long, or when the sensitivity of the human body is high. For example, sulfonamides can cause hematuria; streptomycin, kanamycin, neomycin, etc. can cause dizziness, tinnitus, deafness, etc.; heptomycin, chloramphenicol can cause aplastic anemia, leukopenia; neomycin, tetracycline can also produce damage to the liver and kidneys, etc. 4, dependence and addiction: often taking certain drugs, such as codeine, sleepytone, etc., can cause dependence or addiction to drugs, after discontinuing use can produce a series of Psychological and physical adverse reactions. Another example is the long-term use of painkillers and Remifentan to sodium aminosalicylate, which can easily produce dependence and reduce the effectiveness of the drug.