The most dangerous time of cephalosporin allergy varies from person to person, usually about 2-3 days of active anti-allergy treatment can pass the dangerous period, but the time required varies with individual physique. Usually, acute allergic symptoms may occur during or within a few hours after cephalosporin infusion. For mild skin itching and rash, it is sufficient to stop using cephalosporins, which usually do not cause great harm to human body. However, if there is obvious itching of skin, or even difficulty in breathing, wheezing, panic, etc. then immediate rescue is needed. Generally, after 2-3 days of active anti-allergy treatment, the dangerous period can be passed and recovery can be obtained in about a week. However, if the patient is not rescued in time, or if the patient has a special constitution, he or she may die of anaphylaxis. In addition, when a patient has a negative cephalosporin allergy test, an allergic reaction may still occur. Therefore, it is also recommended to closely observe any physical discomfort when applying cephalosporin, and to abstain from alcohol when using cephalosporin.