Immunity is an important defense function of the body to exclude foreigners and to purify and stabilize itself for self-protection. The body’s immune defense system generally consists of three lines of defense: The first line of defense is a mechanical barrier that prevents the invasion of pathogenic microorganisms. The antibacterial substances in the sweat and sebum of the skin catch pathogenic microorganisms and block their invasion into the body. The luminal mucosa of the trachea and bronchi secretes mucus to break down the cell walls of invaders, and the cilia of the trachea oscillate to exclude invaders. Stomach acid and normal intestinal flora fight pathogenic microorganisms that enter the digestive tract. The blood-brain barrier prevents pathogenic microorganisms from entering brain tissue and serves to protect the brain. The placental barrier of pregnant women protects the fetus from maternal infections. Members of the second line of defense are phagocytes and various antibodies (immunoglobulins) Various antibodies (immunoglobulins) are missiles in the body that search for enemies, target invasion targets and trigger an immune response; phagocytes are then responsible for engulfing and cleaning up the enemy. The third line of defense is composed of many immune organs Among the members of this family are the collection of lymph nodes, spleen, bone marrow, thymus, tonsils, appendix, etc.: they have lymphatic fluid and blood, a circulatory passage system, and their task is to block and kill the incoming pathogenic microorganisms before they multiply. Human immunity is divided into two types: natural immunity by birth and acquired specific immunity. The former type of immunity is handed down from the ancestors and is equivalent to a standing defense force, responsible for the basic immune protection for the normal functioning of the human body. But if you encounter new viruses such as hepatitis B, SARS, etc., the natural immunity of the human body does not have the ability to recognize these viruses, they come in and replicate in large numbers, people have to get sick. This is when the human immune system also has to “fight back” and fight with the virus, people with high fever is the immune system and germs and viruses are fighting performance. The natural immunity of the human body, through the battle with unfamiliar viruses, has produced immunity specifically against such viruses, that is, acquired specific immunity. Between natural immunity and specific immunity, some people are defeated by viruses and become ill or even lose their lives, while others “survive” and gain specific immunity, and when such viruses attack again, they will take the initiative to fight and keep the enemy out. This is the principle of the vaccine, children in the safety of the premise of planting cowpox, so that he developed specific immunity, when the smallpox virus really came, the specific immunity will work to protect the body from harm. One type of specific immunity can only deal with one type of virus, for example, planting cowpox will not prevent measles. Therefore, the most effective way to prevent certain new viruses that the body does not recognize is to develop a specific vaccine. The specific vaccine is given directly to the human body, which can produce specific antibodies to specific pathogenic microorganisms, and is a useful supplement to the human immune system. Thus, it is clear that the strong function of the human immune system determines the health of the person. If the immune function is weakened, people are vulnerable to infection by bacteria, viruses, fungi and various other microorganisms, and also easy to become members of the population with a high incidence of tumors and cancer, and more serious if their immune function is completely lacking, such as acquired immunodeficiency syndrome people are unbearable. Low immunity is not good for the body, so is the higher the immunity the better? The answer is of course no! Because if the body’s immunity exceeds the normal level (that is, in the “allergic” or “hypersensitive” state), especially in the case of immune system disorders, the immune system will treat the normal cells in the body as ” foreigners” and kill them, thus leading to immune damage to muscle tissue. So, “allergy” simply means being allergic to a substance. When you eat, touch or inhale a substance, your body overreacts, resulting in an allergic disease (also known as “allergic disease”). Allergic rhinitis is a typical allergic disease. In addition, bronchial asthma, lupus erythematosus, rheumatism and other autoimmune system diseases are also examples. Since a patient with allergic rhinitis is already in a “hypersensitive” state, of course, he should not be given immunity, otherwise it may aggravate the patient’s allergy symptoms. With the improvement of people’s living standards, spending money to buy health has become a consensus, but some people rely excessively on immune preparations such as propyl globulin and interferon, thinking that this will improve the immunity of the human body, in fact, there is a bias in this understanding. Because the human immune system is like a spring, proper pressure will make the elasticity better; and if the pressure is applied for a long time, then the elasticity will be greatly reduced. Under normal circumstances, the human immune system will automatically adjust the body’s immunity to an appropriate level. Long-term injection of antibodies from outside can maintain the immunity at a high level for a certain period of time, but this will make the body’s own immune system less active. In this case, once the injection of immune preparations and other drugs is stopped, the body’s own immune system, which has rarely been mobilized for a long time, will not function normally, and the immunity of the human body will be greatly affected.