Penicillin allergy belongs to type I allergic reaction, which is also called rapid allergic reaction, also known as type I hypersensitivity reaction. It refers to the phenomenon that the reentry of the allergen into the human body causes the combination of antigen and antibody in the body, leading to the phenomenon of allergy in the body, for example, the patient will have an increase in vascular permeability, excessive contraction of smooth muscle, and hypersecretion of glands, leading to anaphylaxis in the patient. Firstly, there will be peripheral allergic macules, papules, urticaria, itching, redness, swelling, heat and pain of the skin, and secondly, there will be congestion of the larynx and edema of the larynx. In severe cases, it may also cause a drop in blood pressure, rapid pulse, pallor, and clammy extremities. Finally, symptoms of anaphylactic shock such as unconsciousness, oliguria and anuria will appear. Therefore, once a patient develops a type I allergic reaction of penicillin allergy, desensitization treatment must be carried out rapidly.