The cleaner you are, the less you will get sick. !

Study on asthma and environmental microorganisms-also on hygiene hypothesis. The human body can be regarded as a small ecosystem. In the small universe of the human body, besides the human body itself, there are many invisible "microorganisms" living together. The normal operation of human physiological function depends not only on the normal operation of its own organs, but also on the "healthy" growth of many innate microorganisms in the human body. For a long time, the general public's idea is that "diseases are caused by bacteria, and reducing exposure to bacteria can reduce the occurrence of diseases." Therefore, the parents of modern families keep the family environment spotless, thinking that if the environment is clean, there will be fewer bacteria (microorganisms) in the environment, fewer bacteria, and fewer chances for children to get sick. This logic is indeed effective in many diseases, such as many diseases spread through the "fecal-oral route" such as parasites, bacillary dysentery, cholera, hepatitis A, rotavirus and so on. Have been greatly improved. However, with the development of industrial civilization and the westernization of lifestyle, the problem of asthma affecting modern children is increasing day by day. Microbes and allergic diseases Although the etiology of allergic diseases such as asthma is not completely clear at present, it is found that there is a strong correlation between environmental microorganisms and the occurrence of allergic diseases in human beings: 1. "mode of production" will affect the risk of allergic diseases in newborns: the risk of allergic diseases in children born by caesarean section is greater than that in children born naturally through the birth canal. Scientists speculate that this is because children born naturally through the birth canal will be exposed to more kinds of bacteria in the mother's birth canal than children born by caesarean section. 2. Improper use of antibiotics in infancy will increase the risk of asthma: If babies have taken antibiotics to treat non-respiratory infections before the age of one, their risk of asthma before the age of seven will be greater than that of babies who have not taken antibiotics. Scientists speculate that this is because improper use of antibiotics will make the flora in the baby's intestine ecologically unbalanced. 3. Children who grow up in a family with pets have a lower risk of asthma: before the baby is one year old, if there are people with dogs at home, the probability of asthma will be smaller than those without dogs. Scientists speculate that this is because dogs can bring bacteria to the family. If there are no dogs at home, the chances of children receiving bacteria will be reduced. 4. Bacteria in human body can protect children from asthma: Helicobacter pylori, an ancient bacteria in human body, has an important influence on human physiological health. Scientists speculate that this is because Helicobacter pylori can protect human body from allergic diseases by activating regulatory T cells (immune cells with allergic and autoimmune functions). 5. The higher the exposure of environmental microorganisms, the lower the risk of asthma: Two research reports published in the New England Journal of Medicine 20 1 1 pointed out that the more farm-specific bacteria and molds in the family environment of children living on farms, the greater the diversity of microorganisms in the environment, and the lower the risk of asthma for children. Compared with children who don't live near the farm, the risk of asthma of children who grow up on the farm is greatly reduced by 5 1%. Immunity will be affected by eating habits, physical condition (obesity), drugs, stress, environmental cleanliness (exposure to microorganisms) and even lifestyle (westernization, sedentary, less exercise). From the above observations, we can know that exposure to environmental microorganisms is very important for infants to develop a normal immune system. Exposure to more diverse microorganisms in infancy (especially before one year old) will help children's immune system mature, and the risk of allergic diseases will be greatly reduced when they grow up. However, how do microorganisms in the environment affect the maturity of human immune system? How does it cause allergic diseases? "hygiene hypothesis" Professor David P. Strachan found that the incidence of hay fever (allergic rhinitis) and eczema (allergic dermatitis) in children who grew up in large families (many family members) was lower than that in only children. Professor Strachan put forward a hypothesis about this phenomenon: "Children who grow up in a big family have more chances to get sick through mutual infection with their brothers and sisters in the family, but on the other hand, these diseases can have a protective effect and reduce their chances of suffering from allergic diseases in the future. Therefore, when modern children are young, due to the higher requirements for environment and personal hygiene, their chances of contact with environmental microorganisms are reduced, so that their immune system cannot receive enough environmental microorganisms, so they cannot develop appropriate tolerance to allergens in the environment. This may be why children's growing environment is cleaner, but the incidence of allergic diseases is increasing. Dr Erika von Mutius, a German epidemiologist, conducted another study on the correlation between allergic diseases and environmental microorganisms in the late 1990s1to study the influence of air pollution on asthma. Her research results show that the proportion of children suffering from allergic diseases and asthma in East Germany with serious environmental pollution is far less than that in West Germany who live in a cleaner environment. After analysis, Dr. Mutius said: If children can come into contact with more other children or animals, they will have the opportunity to come into contact with more diverse environmental microorganisms, and these children's immune systems will have more tolerance to these environmental allergens. Although the cause of asthma is still not fully understood, these two important research reports have the same discovery: if children are not exposed to environmental microorganisms in childhood, the maturity of human immune system will be affected, thus increasing the probability of allergic diseases when children grow up. This theory is the famous "health hypothesis". But why can an unsanitary living environment prevent allergic diseases? The theoretical basis of "Hygiene Hypothesis" is that many receptors on cells can obtain immunity through contact with environmental microorganisms and human bacteria, which promotes and regulates the maturity of human immune system and contributes to the balanced development of type I and type II helper T cells. Although researchers have found that allergic diseases are related to the exposure of environmental microorganisms, this theory partly explains why there are more and more people with allergic diseases in the more modern and westernized countries, but what kind of bacteria are related to allergic diseases? What time? What is the most appropriate microbial exposure (species)? None of them has been decided yet. Immune Mechanism of Allergic Diseases/Asthma Lymphocytes in the human immune system can be divided into two groups, one is B cells, whose main function is to produce antibodies, and the other is T cells, which have the function of regulating the operation of the immune system. According to different functions, T cells can be divided into type I helper T cells (Th 1 cell) and type II helper T cells (Th2 cells). Th 1 cells secrete cytokines such as interferon-γ (IFN-γ), interleukin -2 (IL-2) and lymphotoxin (TNF-β) after activation, which has physiological functions of activating macrophages and producing cell-mediated immunity, and plays an important role in fighting intracellular pathogens and autoimmune diseases. Some chronic inflammatory immune diseases, such as multiple sclerosis, 1 diabetes and rheumatoid arthritis, are all caused by the overreaction of Th 1 cells. On the contrary, Th2 cells are important immune cells involved in inflammation, allergic reaction and resisting the invasion of extracellular parasites. After activation, TH2 cells will secrete cytokines such as interleukin 4, 5, 6, 10 and 13(IL-4, 5, 6, 10, 13), which has the tendency of activation. Under normal circumstances, these two kinds of helper T cells will regulate and antagonize each other to maintain the balance and stability of the immune system. If the activity of Th 1 cells is too high in vivo, it will cause autoimmune diseases. Conversely, if the activity of Th2 cells is too high, it will cause allergic diseases. The gastrointestinal tract of newborn infants is sterile, and Th2 cells are the main immune response. However, with the influence of the surrounding environment, such as the type of food ingested by pregnant mothers, the type of microbial colonies in the birth canal, and the type of food fed (breast milk or formula milk), the Th2 cellular immune response in the intestine of newborns will gradually decrease at about one year old and turn into the form of Th 1 cellular immune response. It is found that exposure to environmental microorganisms in childhood can induce Th 1 cells related to anti-infection to become active and inhibit Th2 cells related to allergy. On the other hand, if children are short of microorganisms during this period, it will interfere with the transformation of Th2 to Th 1 cellular immune response, and make Th2 cells related to allergy continue to overreact, leading to imbalance of immune tolerance and so-called "allergic constitution". * * * Symbiont S, like human immunity, feeds hundreds of people. Similarly, bacteria can be divided into "good bacteria" and "bad bacteria". The relationship between living microorganisms and human health has attracted more and more attention. Since 2007, the National Institutes of Health (NIH) has started the Human Microbiology Project, one of whose goals is to decode the microflora of human intestinal microorganisms. With the increasing knowledge of microbiology, it is estimated that at least thousands of bacteria coexist with the human body, with the total number exceeding 10 trillion. There are more than 400 kinds of bacteria in human intestine, which can not only help human digest food, provide nutrition to promote human health, but also play a key role in regulating human immunity. For example, some intestinal probiotics, such as Lactobacillus or Bifidobacterium (or Bifidobacterium), have been proved to reduce intestinal pH by (1) producing organic acid (lactic acid), and (2) competing with other bacteria for nutrients and living space. (4) Enhance the host's immune response to pathogens! Intestinal bacterial cells can not only activate the lymphatic system through intestinal lymph nodes, but also activate macrophages through cytokines such as interleukin -8 (IL-8) and tumor necrosis factor (TNF) secreted by intestinal cells. ) and other ways to promote the growth of "beneficial bacteria" and inhibit the growth of "germs". Once the bacteria in the intestine are out of balance (such as after using antibiotics), it will cause human discomfort. Too much and too little-the contradiction of "hygiene hypothesis" Although "hygiene hypothesis" provides many important clues for the cause of allergic diseases, it is relatively uncertain about "asthma". In fact, some studies have shown that the factors that the "health hypothesis" thinks can prevent allergic diseases may be the chief culprit of non-allergic asthma. For example, childhood respiratory tract infection may help prevent future asthma, but it may actually be an important risk factor for asthma. For example, according to the "hygiene hypothesis", infection will bring protection, so a high infection rate should be accompanied by a low incidence of asthma. However, recent public health epidemiological studies have found that children living in Latin America with relatively poor sanitary conditions have a higher incidence of infectious diseases, but the incidence of asthma is much higher than that of children living in Western Europe with relatively good sanitary conditions. In addition, a transnational study shows that the incidence of asthma varies greatly among European countries with similar sanitary conditions. These results show that there are other more important factors leading to asthma besides "environmental hygiene" conditions. Table 1. Allergy: the immune system of allergic people will be particularly sensitive, and it is easy to have a violent reaction because of a little * * * in the environment. Heredity: Parents are allergic, and children are prone to inherit the same physical environment: temperature, humidity, air pollution (cigarettes, automobile exhaust, nitrogen dioxide, ozone, sulfur dioxide), various chemicals (perfume, paint), common allergens: dust mites, cockroach excrement, animal dander, pollen, etc. Common food allergens: milk, eggs, shellfish, fish, pollen, etc.