The onset of action of I.V. human immunoglobulin is usually within 15 minutes, but the specific onset of action may vary somewhat between manufacturers. Generally speaking, take lyophilized HIg as an example, the plasma level of IgG peaks rapidly after intravenous injection in about 15 minutes, that is, the drug has taken effect within 15 minutes after injection, and the half-life is in 3~4 weeks. The method of intravenous injection of human immunoglobulin is a kind of passive immunotherapy, which can achieve direct neutralization of toxins and kill bacteria and viruses, and has a certain effect on the prevention of bacterial and viral infections. However, there are certain contraindications to the use of human immunoglobulin, i.e., anyone who is allergic to human immunoglobulin, or selective IgA deficiency with anti-IgA antibodies needs to be prohibited from using the drug, and attention needs to be paid to observing the occurrence of adverse reactions, such as headache, panic, nausea and so on when using the relevant medicines. The use of the drug should be carried out under the supervision of a doctor.